A Rudimentary Treatise on the History, Construction, and Illumination of Lighthouses, Volumes 1-3 |
Other editions - View all
Common terms and phrases
adopted angle angle of incidence annular apparatus Argand Argand burner Argand lamps arrangement Augustin Fresnel axes beam Bell Rock Bell Rock Lighthouse belt burner catadioptric catoptric light centre of curvature coast colza oil combustion concave cone consideration convex course curve cylindric diameter dioptric lights direction divergence Eddystone effect Engineer equal feet fixed lights flame flashes focal distance frame Fresnel frustum glass height High Holborn illumination inches incident inclination instrument keepers lamp lantern lens lenses less Light-room Lightkeeper luminous means millimètres mode Northern Lighthouses observer obtained parabolic paraboloïdal mirror parallel placed plane Plate portion position principal focus Principal Lightkeeper prisms produced radius radius of curvature rays reflecting surface reflectors refraction refractive index refractors revolving lights rings Robert Stevenson round shadows shewn shews side sin² Skerryvore spermaceti spherical stone tance tangent tion tower vertical axis waves wick
Popular passages
Page 160 - ... of the ventilating chimney enters into the cowl or head of the lantern. With this arrangement, it is found that the action of the. ventilating flue, is to carry up every portion of the products of combustion into the cowl ; none passes by the cone apertures, out of the flue into the air of the lantern, but a portion of the air passes from the lantern by these apertures into the flue, and so the lantern itself is in some degree ventilated. The important use of these cone apertures is, that when...
Page 160 - When the chimney is put together, the upper end of the bottom piece is inserted about | an inch into the cone of the next piece above, and fixed there by three ties or pins, so that the two pieces are firmly held together ; but there is still plenty of airway, or entrance into the chimney between them. The same arrangement holds good with each succeeding piece. When the ventilating chimney is fixed in its place, it...
Page 54 - Stevenson, were most imperfect, not only in point of efficiency and power, but also as respects the distinction of one light from another; an object which, on a difficult and rugged coast, may be considered as of almost equal importance with the distance at which the lights can be seen...
Page 100 - ... in a minute, as may be required, a light gradually increasing to full strength, and in the same gradual manner decreasing to total darkness, its appearance is extremely well marked. The...
Page 101 - ... its name. The intermittent light is distinguished by its bursting suddenly on the view, and continuing steady for a short time, after which it is suddenly eclipsed for half a minute. This...
Page 42 - 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 no work of art more beautiful or more creditable to the boldness, intelligence, and zeal of the artist.
Page 18 - ... narrow space below, to which so many persons were necessarily confined. Yet had we not any loss of either life or limb; and although our labours were prolonged from dawn to night, and our provisions were chiefly salt, the health of the people, with the exception of a few slight cases of dysentery, was generally good throughout the six successive summers of our sojourn on the rock. The close of the work was welcomed with thankfulness by all engaged in it; and our remarkable preservation was viewed,...
Page 13 - ... to the recommencement of the works. For miles around nothing could be seen but white foaming breakers, and nothing heard but howling winds and lashing waves. At such seasons much of our time was spent in bed; for there alone we had effectual shelter from the winds and spray which searched every cranny in the walls of the barrack.
Page 33 - ... on the lowness of its centre of gravity, the general notion of its form is that of a cone, but that, as the forces to which its several horizontal sections are opposed decrease towards its top in a rapid ratio, the solid should be generated by the revolution of some curveline convex to the axis of the tower, and gradually approaching to parallelism with it.
Page 13 - At such seasons much of our time was spent in bed ; for there alone we had effectual shelter from the winds and the spray, which searched every cranny in the walls of the barrack. Our slumbers, too, were at times fearfully interrupted by the sudden pouring of the sea over the roof, the rocking of the house on its pillars, and the spurting of water through the seams of the doors and windows...