While the light was admittedly of a temporary character, the importance of the outpost had been appreciated, and it was determined to erect a permanent light upon the rock for the guidance of those who compass the North of Scotland in order to pass from and to the North Atlantic. It was decided to commence the permanent masonry building the following year, and a gang of men volunteered to stay behind on the rock throughout the winter to complete all the essential preparations for the foundations. Accommodation was available for this staff in a substantial iron shelter, in which they made themselves comfortable for the winter. But it is during this season that the winds from the north, lashing the sea to fury, create huge rollers which thunder upon the base of the pinnacle to crawl up its perpendicular face in the form of broken water and spray. The men standing on the brink often watched these rollers, but never for a moment thought that one would be able to leap to a height of nearly 200 feet and sweep over the rock. The December gales dispelled this illusion very convincingly. One morning the workmen, while breakfasting in their warm shelter, received a big surprise. A terrific blow struck the door, which flew open as if hit by a cannon-ball. It was followed instantly by a three-foot wall of water. The broken wave rushed round the apartment, seething and foaming, and then out again. The workmen were dumbfounded, but had scarcely recovered from the shock when another roll of water came crashing in and gave the apartment another thorough flushing out. One of the Scottish workmen vouchsafed the remark that the man responsible for cleaning the floors that day would be spared his job, but he was silenced when, a few seconds later, another angry sheet of water dropped on the roof of the building and threatened to smash it in. [Illustration: THE NORTH UNST, BRITAIN’S MOST NORTHERLY LIGHT. The tower is perched on the top of a precipitous crag, the light being 260 feet above the sea. Despite this height, the waves often dash over the lantern.] The closing month of that year was particularly boisterous. Time after time when the sea rose, the lighthouse tower was drenched in water. One might think it impossible that a wave could get up sufficient impetus to mount a height of 200 feet; but this experience offered conclusive testimony to the contrary and to the immense power of the waves when they have an uninterrupted run over several hundred miles of open ocean. In a way, the terrifying experience of these marooned workmen was invaluable. They reported the bare facts to the engineers upon the first opportunity, and this intelligence brought about a revision in the designs for the permanent masonry structure.