In July 1841 the masonry had been carried to an elevation which rendered impossible the further employment of the stationary crane. As a substitute the balance crane was introduced—that beautiful machine, invented at the Bell Rock, which rises simultaneously with the edifice it assists to raise. Thanks to this new auxiliary, the mass of masonry completed in the season of 1841 amounted to 30,000 cubic feet, more than double the mass of the Eddystone, and exceeding that of the Bell Rock lighthouse. Such was the delicate precision observed in the previous shaping and fitting of the stones, that after they had been regularly fixed in their respective places, the diameter of each course did not vary one-sixth of an inch from the prescribed dimensions, and the height was only one inch more than had been determined by the architect in his previous calculations. On the 21st of July, the steamer saluted with its one gun the disembarkation of the last cargo of stones intended for the lighthouse. On the 10th of August the lantern arrived, which was hauled up to its position, and duly fixed; a temporary shelter from the weather being also erected for it. The summer of 1843 was devoted to pointing the external masonry—a wearisome operation, conducted by means of suspended scaffolds—and to the completion of the internal arrangements. And at length, on the 1st of February 1844, the welcome light of the Skerryvore pharos blazed across the waters of the stormy sea. The illuminating apparatus adopted was the dioptric, and identical in all respects with the apparatus supplied a few years before to the Tower of Cordova. It is a revolving light, whose full brilliancy is apparent only once in a minute. Elevated 150 feet above the sea level, it is visible at a distance of eighteen miles. * * * * * Such is the stirring history of the Skerryvore lighthouse. The reader will think, perhaps, that it differs but little from that of the Bell Rock and the Eddystone. Nevertheless we could not pass over it in silence, for it completed a work which may fitly be called “the art of building lighthouses in the open sea”—an art entirely unknown before the days of Smeaton, and Robert and Alan Stevenson—three men of whom Ocean, if it could translate into words the “rhythmical smile” of its summer calm, or the harsher accents of its equinoctial wrath, might say with the poet,— “Great I must call them, for they conquered me!” [Illustration] CHAPTER V. NORTH UNST, 1854.—SUNDERLAND, 1841. The erection of the North Unst tower, completed in 1854, offered no difficulties comparable to those which tested the skill and perseverance of the builder of the Bell Rock; yet, not the less, it is interesting as one of the most important results obtained by our English engineers. As our illustration shows, it stands rooted on an isolated reef, near the Shetland Isles, whose elevation above the sea is estimated at 200 feet.