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adopted advantage already angle apparatus appear applied arrangement axis base beam Bell building burner called cause centre common cone consideration construction continually course curve described determined diameter difference dioptric direction distance divergence effect employed Engineer equal experience face feet fixed lights flame flashes focal focus frame Fresnel give given glass greater height horizon illumination inches incident inclination increase iron lamp lantern length lens lenses less lighthouse Lightkeeper lower manner means measured mirror mode nature nearly necessary noticed object observer obtained once parallel passing placed plane Plate portion position practical present principal produced radius rays receive reference reflected reflectors refraction render result revolving lights rings Rock round seen serve shadows shewn shews side similar situations Skerryvore stone sufficient surface tion tower various vertical waves whole wick zones
Page 138 - length, but divided into three or four pieces ; the lower end of each of these pieces for about 1£ inch is opened out into a conical form, about 5£ inches in diameter at the lowest part. When the chimney is put together, the upper end of the bottom piece is inserted about
Page 18 - It consists of a central belt of refractors, forming a hollow 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 168 - When stores of any kind are to be landed for the use of the Lighthouse, the Lightkeepers shall attend and give their assistance. The Principal Lightkeeper must, upon these occasions, satisfy himself, as far as possible, of the quantity and condition of the Stores received, which must be duly entered in the Store-book and Monthly Return-book.
Page 115 - with the greatest of those inventors who extend the boundaries of human knowledge, will thus, at the same time, receive a place amongst those benefactors of the species who have consecrated their genius to the common good of mankind ; and, wherever maritime intercourse prevails, the solid advantages which his
Page 18 - was to that of the seven upper tiers of mirrors of the first order, as 140 to 87. Nothing can be more beautiful than an entire apparatus for a fixed light of the first order,
Page 163 - The Lightkeepers shall keep a regular and constant Watch in the Light-room throughout the night. The First Watch shall begin at sunset. The Lightkeepers are to take the Watches alternately, in such manner that he who has the first Watch one night shall have the second Watch next night. The length or duration of the
Page 107 - sufficient to discourage us from attempting to improve the visibility of fixed lights in the manner proposed by Captain Hall, even supposing the practical difficulties connected with the great centrifugal force generated by the rapid revolution of the lenses to be less than they really are.