Fig. 5.—A Four-Panel Light.
The ray thrown through each panel is six times as powerful as the beam thrown through a twenty-four panel apparatus.
But the Frenchman’s ingenious invention has been developed out of recognition. To-day only the fundamental basis is retained. Marked improvements were made by Mr. Alan Stevenson, the famous Scottish lighthouse engineer. In fact, he carried the idea to a far greater degree than Fresnel ever contemplated, and in some instances even anticipated the latter’s subsequent modifications and improvements. This was demonstrated more particularly in the holophotal revolving apparatus, the first example of which he designed for the North Ronaldshay lighthouse in 1850, a similar apparatus being devised some years later by Fresnel. In 1862 another great improvement was made by Mr. J. T. Chance, of the well-known lighthouse engineering firm of Birmingham, which proved so successful that it was incorporated for first and third order apparatuses in the New Zealand lights designed by Messrs. Stevenson in the same year.
Fig. 6.—Single Apparatus in Four Panels.
(By permission of Messrs. Chance Bros. and Co., Ltd.)
The French and British investigators, however, were not having things entirely their own way. The United States played a part in these developments, although they did not enter very successfully into the problem. The first lighthouse at Boston Harbour carried candles until superseded by an ordinary lamp, which was hung in the lantern in much the same way as it might have been suspended behind the window of a private dwelling. An inventor, Mr. Winslow Lewis, who confessed that he knew nothing about lighthouse optics, patented what he called a “magnifying and reflecting lantern” for lighthouse work, which he claimed was a lamp, a reflector, and a magnifier, all in one. It was as crude a device as has ever emanated from an inventive brain, but the designer succeeded in impressing the Government so effectively that they gave him £4,000, or $20,000, for his invention. The reflector was wrought of thin copper with a silvered surface, while the magnifier, the essence of the invention, was what he called a “lens,” but which in reality comprised only a circular transparent mass, 9 inches in diameter, and varying from 2½ to 4 inches in thickness, made of bottle-green glass. The Government considered that it had acquired a valuable invention, and was somewhat dismayed by the blunt opinion of one of its inspectors who held contrary views concerning the magnifier, inasmuch as he reported cynically that its only merit was that it made “a bad light worse.”
Fig. 7.—Double Flashing Apparatus: Two Panels and Mirror.