The Lighthouse Stevensons - Bella Bathurst [84]
Alan, therefore, had to find the best method of constructing a tower whose shape and weight resisted the sea in the most efficient way possible. His first step was to ensure that the centre of gravity was as low as possible; his second was to distribute the weight of the stones to optimum effect, and his third was to build high enough to give the waves least chance of leverage. With all of this in mind, he designed a tower 138 feet high and weighing 58,580 tons, with nothing that the sea could get a grip on but a narrow cornice at the base of the lantern. The Bell Rock, by comparison, was 100 feet high, and 28,530 tons in weight; the Eddystone 68 feet and 13,343 tons. His final choice was an aesthetic one. Having decided on the most practicable design for a light, he was left with four possible formulas for the shape of the tower. He chose a hyperbolic curve because it pleased his eye. It was, he said, ‘a simple and almost severe style’. He designed it perfectly, but also made it beautiful, just for the sake of it.
In one sense at least, Alan’s plottings were not conducted alone. All his choices were made with two influences in mind: the ghost of Smeaton and Robert. Alan proved himself strong enough for both of them, disputing Smeaton’s wisdom that any sea-tower should be built on the principle of an oak tree, and dispensing, through shrewd physics, with his father’s dovetail joints. Alan reasoned that the sheer weight of the tower coupled with the even distribution of its tonnage would dispense with the need for dovetails in all but the upper courses. In Skerryvore’s case, none of the tower would be underwater at high tide, so there was little fear of water dislodging the masonry while it was being constructed, and Alan, conscious of making savings where possible, concluded that the jigsawed joints at the Bell Rock were both expensive and unnecessary on Skerryvore. Considering Robert’s involvement in the planning of the light, it must have taken some courage for Alan to defy his father so directly. Robert kept a keen eye on Alan’s progress throughout the works. Alan pacified him with honesty, diplomacy and the occasional sin of omission. He did, however, draw upon his father’s work in other respects. Robert’s idea of building a temporary workmen’s barracks on the rock to keep stores and give shelter to the workmen seemed to Alan to be essential on Skerryvore where the foul seas often delayed the boat trips back to Hynish. ‘So important, indeed, did this object appear to me, that I was at times apt to look upon it as an indispensable step towards ultimate success,’ Alan confessed. The barracks was to be built on much the same lines as his father’s version – six sturdy wooden pillars trussed together with iron bands supporting a rocket-shaped cabin.
On 5 May 1838 Alan sailed out from Greenock with a cargo of materials on his way to Hynish and the start of the works. Some progress had already been made. Sixty fine blocks of Tiree gneiss had been quarried, the workyard was almost completed and a gunpowder magazine had been prepared. Alan spent a month at Hynish checking stores, finding new sources of stone and instructing the workmen. It wasn’t until 28 June that Alan finally reached the rock, and was left there while the row-boat returned to the tender for the rest of the working party. Stuck alone on Skerryvore and watching the waves lap higher with the tide, Alan felt a thrill of morbid fear. ‘I could not,’ he wrote later, ‘avoid indulging in those unaccountable fancies which lead men to speculate with something like pleasure upon the horrors of their seemingly impending fate. These reflections were rendered more impressive by the thought that many human beings must have perished amongst these rocks.’ Alan was not usually inclined