The immediate result of this visit on the mind of the writer and of Mr Haldane, was a firm conviction of the practicability of erecting a building of stone upon the Bell Rock; and from that moment the idea of a pillar-formed light-house was rejected, as unsuitable to the situation. This opinion was chiefly founded upon the area or extent of the part which dried, or was exposed to view in the spring-tides, being found to measure about 280 by 300 feet, and consequently affording a sufficient space for a foundation, and even a degree of shelter from the force of the waves, for the lower courses of a building.
Pillar-formed building compared with one of stone.
The depth at high-water upon the Bell Rock was much against the design of a building with pillars, as a vessel drawing 12 feet water, and loaded with 100 or even 200 tons, may come with full sail against any erection made there. Were such a circumstance to happen to a pillar-formed building, and a ship to get thus entangled among the openings of the under part of the light-house, there is little doubt that the event would prove fatal to a building of that construction, however strongly framed. On the contrary, supposing a vessel to strike a building of stone, under these circumstances, it is not at all likely, that she could have any effect upon a mass of matter extending to 2000 or 3000 tons, so as to injure such a fabric.
Author’s designs and models of a stone-building.
Under these impressions, the writer, after his first visit to the Bell Rock, in the year 1800, made a variety of drawings, and constructed new models for a building of stone, shewing various methods of connecting the stones, by dove-tailing them laterally, like those of the Eddystone light-house, and also course to course into one another perpendicularly. Other methods were likewise modelled, for connecting the whole building in a more simple manner, by means of joggles, or square blocks of stone, and also by dove-tailed bats of iron cased in lead, as delineated in the various designs of [Plate VII.] These plans and models were duly submitted to the Light-house Board, accompanied with estimates of the expence, amounting to the maximum sum of L. 42,685, 8s.
Mr Telford requested to visit the Bell Rock.
Sir William Pulteney having taken an interest in forwarding a bill for this measure in Parliament in the year 1803, gave Mr Thomas Telford, engineer, instructions to inquire into the circumstances of the Bell Rock, in the course of his journey to the Works of the Caledonian Canal. Mr Telford had accordingly taken some preparatory steps for making a Design; and, with this view, he had engaged Mr Murdoch Downie, author of several Marine Surveys, to accompany him to the Bell Rock. But the weather proved unfavourable at the time for effecting a landing upon the rock; and, the bill then in progress having been withdrawn before another opportunity occurred, Mr Telford’s visit was not resumed.
Mr Downie’s pillar-formed Light-house of Stone.
Mr Downie, however, who had previously been upon the rock, when making his Nautical Survey of the Eastern Coast of Scotland, prepared a drawing and an estimate of the expence of erecting a light-house upon it, which he stated at about L. 29,000. His light-house was to have consisted of eight columns of stone, of an elliptical or egg form, as he expressed it, ranged round a common centre, having the longer axis and smaller end towards a circular column in the centre of the plan. These columns were to support a circular building of stone for the habitation of the light-keepers and the site of the light room. By this plan it was meant to give less resistance to the waves. But it did not seem to be well adapted for the situation, as it wanted that solidity and unity of parts which are so essential to the stability of a building upon a sunken rock. Such a work would have been of difficult execution. It would have required similar apparatus with the solid masonry for its construction, and while in progress, it would have been in greater danger of being destroyed than a solid fabric. There seemed, therefore, upon the whole, to be but two opinions as to the proper description of a light-house for this situation, viz. either that it should be constructed of iron, as was maintained by Captain Brodie, or of solid masonry, as proposed by the writer.