After some alterations of the Cordouan wood-fire, the mariners complained that they could not see the light at a distance of tNs leagues, as formerly. But Smeaton informs us, that the coal-fire of the Spurn Point lighthouse, at the mouth of the Humber. which was constructed on a good principle for burning, had been seen thirty miles off.
The only exceptions to the fires were the noble Eddystone lights, which then exhibited a chandelier of twenty-four wax candles, five of which weighed 21bs., and the Liverpool light houses, which had oil lamps, with rude reflectors.
The coal lights are now quite abolished. The last was at one station belonging to Sweden, on the little island of Nidingen, on the east side of the Categat, near the entrance to the Baltic sea. These were two light towers, showing coal fires, but surrounded by sides of glass, to shelter them from the wind, and open at the top. They were altered at the beginning of the year 1846.
The introduction of the Argand lamp was the first great advance towards the perfection of lighthouses. This improve ment in artificial light was the greatest, previous to the intro duction of gas. It was discovered by M. Argand, a citizen of Geneva, about 1780 or 1785. It has remained as he left it, and in principle appears as perfect as can be looked for. Its perfection as an experiment was almost accidental. The younger brother of Argand thus describes its accidental dis covery. "My brother," he says, "had long been trying to bring his lamp to bear. A broken-off neck of a flask was lying on the chimney-piece ; I happened to reach it over the table, and to place it over the circular flame of the lamp; immediately it rose with brilliancy. My brother started from his seat in exstasy, rushed upon me with a transport of joy, and embraced me with rapture." Thus originated the Argand lamp.
On the introduction of a more efficient means of illumina tion, and the consequent abandonment of the coal fires, light houses assumed a more important position in maritime Milli rs, and they were, accordingly, largely increased in number.
This extension rendered necessary another improvement— the means of readily distinguishing one light from another. Although many suggestions have been made for doing this more elll..etually—some practicable, others not so. and some are in actual operation—this part of the science is tar from being in a perffict state. Much remains to be done, before the mariner can be certain of determining, by its distinctive features, each light when seen.
The variety r,f lights that have been proposed and experi mented on for lighthouse purposes is very great, particularly, we may mention, the Drummond, the electric, voltaie, &c., but few have stood the test of experience ; and the lamps now in universal use are still but modifications of the original Argand burner.
Amongst the means for increasing the intensity of light, the use of reflectors is most' important. In the year 1786, reflectors and oil lamps were first proposed at a meeting of the Scottish lighthouse commissioners. The first metallic reflectors used in the northern lighthouses were constructed by Mr. Thomas Smith, of Edinburgh. The figure was given to them by a plaster mould, and the cavity was afterwards filled in, by means of cement, with small facets of mirror glass. This must have done its work very imperfectly, although the general figure was capable of considerable accuracy. In 1S03, the first polished metal reflectors used in Scotland, were placed in Inch-Keith lighthouse ; since then, various slight alterations and improvements have been made, but substantially, the system of illuminating light houses remains the same.
We cannot conclude this article without acknowledging our obligations in its preparation to the valuable paper on lighthouses, &c., by Mr. Findlay.