Tour d’Ordre, the, of Boulogne, built by Caligula, 130; early history of, 31; destruction of, 32; the tribute connected with, 32; description of its remains, 35, 36; the worthy substitute for, 36, 37. Tradition, how carelessly accepted, 43. Trinity House, history of, summarized, 50-53; interior organization of, 53, 54; functions of its members, 54; the building, described by Esquiros, 58-61. United Kingdom, number of lighthouses in, enumerated, 56. Unst, North, island of, lighthouse at, described, 181. Ventilation for lighthouses, Professor Faraday’s system of, stated, 101, 102. Virgil, the poet, quoted, 196. Vivian, the engineer of Cayenne, on the Enfant Perdu, 250. Vossius, Isaac, story of the Alexandrian pharos, quoted from, 26. Walde, the lighthouse of, referred to, 250. White, Walter, quoted, 193, 194, 200, 201. Whiteside, the engineer of the Smalls lighthouse, an adventure of, 134-137. Wight, isle of, lights of, mentioned, 131. Wilde, Mr., of Manchester, his invention of an electro-magnetic apparatus for lighthouse illumination, 83, 84. Winstanley, Henry, his eccentric genius, 109; the erection of his lighthouse on the Eddystone described, 110-113. Wolf’s Crag lighthouse, the, described, 195, 196. Wordsworth, the poet, on Grace Darling, 281. Zach, the Baron de, cited, 10, 11. [Illustration] [Illustration] List of Illustrations. Eddystone Lighthouse (_Frontispiece_). The Beacon Fire, 1 A Roman Pharos, 15 A Medal of Apameia, 16 Ancient Pharos of Alexandria, 23 Modern Lighthouse of Alexandria, 27 Tour d’Ordre of Boulogne, 33 The Tower at Dover, 39 The Colossus of Rhodes, 45 Trinity House, 58 Lighthouse on a Rocky Headland, 64 Catoptric Apparatus, 72 An Argand Fountain Lamp, 74 Revolving Apparatus on the Catoptric Principle, 75 Annular-built Lens, 78 Electric Apparatus for Fixed Light, 82 Annular Lens of First Order, 85 Diagram, Illustrating Progress of Luminous Ray in a Catadioptric Ring, 87 Fresnel’s Revolving Light, 90 Stevenson’s Holophotal Light, 91 Stevenson’s Fixed Light varied by Flashes, 92 Fresnel’s Fixed Light Apparatus, 93 French Fixed Light Apparatus, 93