The Commissioners of Northern Lights acknowledged the urgent need of a light upon this ridge, but it was realized that its erection would represent the most daring feat of lighthouse engineering that had been attempted up to this time. There was only one point where a tower could be placed, and this was so exposed that the safe handling of the men and materials constituted a grave responsibility. The rock has to withstand the full impetus of the Atlantic waves, gathered in their 3,000 miles’ roll, and investigations revealed the fact that they bear down upon the Skerryvore with a force equal to some 3 tons per square foot. It was apparent that any masonry tower must be of prodigious strength to resist such a battering, while at the same time a lofty stack was imperative, because the light not only would have to mount guard over the rock upon which it stood, but also over a vast stretch of dangerous water on either side. After he had completed the Bell Rock light, Robert Stevenson attacked the problem of the Skerryvore. In order to realize the magnitude of the undertaking, some of the Commissioners accompanied the engineer, but the experience of pulling out into the open Atlantic on a day when it was slightly ruffled somewhat shook their determination to investigate the reef from close quarters. Sir Walter Scott was a member of the party, and he has described the journey very graphically. Before they had gone far the Commissioners on board expressed their willingness to leave the matter entirely in the hands of their engineer. With grim Scottish humour, however, Robert Stevenson insisted that the rock should be gained, so that the Commissioners might be able to grasp the problem at first hand. But after all nothing was done. The difficulties surrounding the work were only too apparent to the officials. They agreed that the expense must be prodigious and that the risks to the workmen would be grave. In 1834 a second expedition was despatched to the reef under Alan Stevenson, who had accompanied his father on the previous occasion, and who now occupied the engineering chair. He surveyed the reef thoroughly, traversing the dangerous channels around the isolated humps, of which no less than 130 were counted, at great risk to himself and his companions. However, he achieved his object. He discovered the best site for the tower and returned home to prepare his plans. His proposals, for those days, certainly were startling. He decided to follow generally the principles of design, which had been laid down by his father in regard to the Bell Rock. But he planned something bigger and more daring. He maintained that a tower 130 feet high, with a base diameter of 42 feet, tapering in a curve to 16 feet at the top, was absolutely necessary. It was the loftiest and weightiest work of its character that had ever been contemplated up to this time, while the peculiar situation of the reef demanded pioneering work in all directions. [Illustration: