[Sidenote: Reflectors of Silvered Mirror-glass.] [Sidenote: Reflectors of Copper, plated with Silver.] [Sidenote: The use of Argand lamps and Spermaceti Oil introduced.] The reflectors of the first of the Northern Light-houses were formed to the parabolic curve, upon principles susceptible of considerable accuracy; their powers were, however, small from their reflecting surfaces being composed of facets of silvered mirror-glass, and one point only of each facet coinciding with the curve of the parabola. As many of the rays are thus lost or weakened by transmission through the glass of the reflector, the light is much less brilliant than when reflected from a metallic speculum of a uniform parabolic figure, of a more white and dense body, such as silver. Another objection to mirror-glass reflectors, is the great number of interstices or subdivisions between the pieces of glass, which unavoidably induces a want of cleanliness and uniformity in the reflecting surface as a whole. The improvement upon this part of the reflecting apparatus, as more recently fitted up, consists in employing sheets of copper, plated or coated with silver, which, with much labour and great nicety of workmanship, are formed as nearly as may be into the parabolic curve,--a subject to which we shall again recur, in treating of the reflectors for the Bell Rock Light-house. Instead, also, of whale oil, and the use of the Common lamp, spermaceti oil, and the Argand lamp, were introduced at Inchkeith. Upon these principles, all the new erections of the Northern Light-houses are constructed; and such of the original light-houses, as require considerable repairs, are directed by the Board to be altered to the improved construction. But the erection of such a light-house as that of Inchkeith, in place of requiring an expenditure of only about L. 1000 like the original establishments, cost upwards of L. 5000. [Sidenote: Inscription on Inchkeith Light-house.] The light-house of Inchkeith having been erected before the late Mr Smith, the author’s predecessor, had retired from the situation of Engineer for the Northern Light-houses, and being the first of the light-houses erected upon the coast of Scotland on the recently improved principles, it is thought proper to give a plan and elevation of the house and offices, in one of the plates of this work, as a specimen of what is considered a very complete light-house establishment. It may also be noticed here, that the elevation of the light-house tower bears a tablet with the following inscription:--“For the direction of Mariners, and for the benefit of Commerce, this Light-house was erected by order of the Commissioners of the Northern Light-houses. It was founded on the 18th day of May, in the year 1803, and lighted on the 1st of September 1804. THOMAS SMITH, _Engineer_.” [Sidenote: Pilots and Shipwrecked Seamen receive shelter.]