" The Light of all nations" was intended to be an iron tower erected by means of an iron caisson, which was to aflitrd the means of forming a substantial foundation. This caisson, the frustum of a cone 30 feet in diameter, and 28 tbet high, weighing about 150 tons, was towed out from Deal by one of I ler Majesty's vessels to its station, about the centre of the Goodwin Sands, on July 27, 1S42. The caisson was made water-tight, in order that, as it settled down, the workmen might be enabled to construct the foundation on the chalk substratum of the sand. This substratum, however, was never reached ; the caisson didttl _own, but not per pendicularly, and after it had been knocked about by several gales of wind, it was found impracticable to carry out the original design, and it was therefore necessarily abandoned. On the wreck of the caisson, however, Mr. Bush succeeded in erecting a smaller shaft, surmounted by a small light-room, and in this room he and his wife remained during a night in the beginning of 18-15.
The lighthouse was never completed. And the Trinity House was at last obliged to interfere, to prevent, from its dangerous situation, its being used as a light-beacon.
Another adaptation of iron to the construction of lighthonses has met with thr greater success, and promises to be of the greatest utility, whether as regards economy, or facility of construction. This is the iron lighthouse designed by Mr. Gordon.
It is rather singular that iron should not have been employed in this form before, when we consider the multi farious variety of purposes to which it is now applied. In the year 1805, however, a east-iron lighthouse was suggested by Mr. Rennie, for the Bell-rock, and also by Mr. Robert Stevenson in 1800. The first tower of this construction, was erected on the eastern end of the island of Jamaica, and another of a similar kind for Bermuda. The latter is 105 feet 9 inches high, formed with iron plates, the entire weight of which is nearly 100 tons. The building has seven stories, and the lower portion is filled in with concrete to the height of 22 feet, to give it stability. Nearly every portion of the edifice is of iron, and the erection of the tower was completed in ten months, finished October 9, 1S45. These lighthouses were constructed in London, put together and erected, and then taken to pieces again and thrwarded to their destination.
The light in the Bermuda lighthouse is from a dioptric first order apparatus, constructed by Messrs. Wilk ins and Son, of Long Acre ; the lenses composing it were made by M. II. Lepante of Paris, and is one of the most efficient and powerful lights in the world.
Having thus slit twii some of the different methods employed in the credit m of lighthouses, and the which modern art has introduced, we now turn to another important part of our subject, that of the illumination of lighthouses.
The first lighthouses, such as the Cordomm, and the North Foreland, were illuminated by open fire-places, or chauffers, placed on the summit of the towers. In the, former, they burnt billets of oak-wood ; and in the latter, coal. It will be readily seen how such arrangements must have perftrined their office. Of course the time at which a lighthouse becomes most serviceable is, during tempestuous weather, and a wind blowing towards the laud, causes that dread of ma•iners—a lee-shore; yet this wind would drive the flames of an open fire away front the very- direction in which they were most required to be seen ; thus the bars of the grate were often nearly melted to leeward, while towards the sea the coals remained untouched by the fire. One advantage, how ever, there certainly was sometimes in the open fire, viz., that, during fog or rain, the glare of the fire was visible by reflection in the atmosphere, though the fire itself could not be seen.
The North Foreland lighthouse, between Ramsgate and Margate will be more fitmiliar to many of our readers than any other, and will serve as an excellent example of the pro gress of illumination. This lighthouse was erected for indi cating the proximity of the Goodwin Sands. The first inti mation we have of its existence is in 1636, in Charles the First's reign, when license was granted to Sir John Meldrum to renew and continue this and the South Foreland light house for the same purpose. At this time it was merely a large glass lantern on the top of a timber-and-plaister house, which was burnt in 1683. Towards the end of the same century, the present tower was partially erected ; a strong octagonal structure, having the iron grate, or chauffe•, for burning coals. From the difficulty of keeping up a proper flame in windy or rainy weather, it was covered about the year 1732, with a sort of lantern, with large sash windows, and the coal fire was kept alight by means of large bellows which the attendants blew throughout the night. This was found not to answer, and the reflected glare above-mentioned was thought desirable. Accordingly, the lantern was re moved, and the fire restored to its original condition. Mat ters went on thus till 1790, when the tower was raised to the height of 70 feet, and further improvements made in the lantern, by the introduction of lamps and other appara tus, hereafter to be described.