In the erection of the Eddystone lighthouse, the dangers and difficulties which were encountered and overcome, owing to the smallness of the surface of the rock, were great and numerous ; and although the surface of the Bc1I-rock was considerably larger. still, being more sunk, and only discovered at low water, the dangers to be encountered were equally great and overwhelming. Owing to the enlarged diameter of the rock, the engineer was enabled to make the masonry of this building more than double the cubical contents of the Eddystone. The following short table will exhibit to our readers the relative dimensions, &e. of the two lighthouses :— • Eddystone. Bell-rock.
Height of the rock, about Level with high Level with low water mark. water mark Height of masonry above the rock .. 70 feet. 100 feet.
Diameter of the first entire course .. 26 feet. 42 feet.
Cubic contents in feet, about 13,147. 28.530 Ascertained.
Expense understood to have been about £21,000. £61,331 9 2 Very early, no doubt, attempts were made to obviate the dangers of this fatal spot ;. and accordingly, tradition reports that the monks of the Abbey of Arbroath erected a hell on the rock, which was to be rung by machinery affected by the flowing and ebbing of the tides, whence the present name of the rock, it is said, took its rise.
After many complaints of the want of a lighthouse, and especially after the violent storm in 1799, during which many ships were driven from their moorings in Yarmouth 'Roads, and even the Downs, and so many of them destroyed on the Scotch coast, that, when the storm subsided all the bays were margined by broken timber, it was at last resolved to construct a lighthouse. A bill for this purpose was passed in I SOti, which enabled the commissioners of the northern Iigdithouses to levy three-halfpence a ton upon all British vessels trading to and from the ports between Berwick and Peterhead, and twice as much upon foreign vessels. The bill also empowered the commissioners to borrow £25,000 from government ; and they had 1'20.000 of accumulated surplus, Whiell showed that the provision of lights had not previously been kept up to the amount of the tax upon navigation. Still, however, this enabled the commissioners to begin the work with a fund of £45,000. While the proposal was in agitation, pro jects for lighthouses were advanced by different individuals; but it was ultimately resolved that the structure should be of stone, somewhat similar to the Eddystone lighthouse, and conducted under the principal superintendenee of the late Mr. Rennie. It was well for the stability of the structure, and the benefit of trade, that this eminent and judicious engineer was appointed, for there were other parties who occasionally interfered in the progress of the work ; and some of the course; of stone intended for, and actually prepared in the workyard at Arbroath, were, for want of central dovetailing, so faulty, that, had they been used, the work could not have stood. These courses of stone were eondeinned by Mr. Rennie, and ordered to be broken up for rubble, as appeared by the signature of Mr. Rennie, on the plans. By the necessary condemnation of these faulty courses of stone, a considerable sum of money was lost, but the stability of the lighthouse was not endangered, which was the grand matter ; and this shows how very careful eminent engineers, who are not constantly on the spot, ought to be, in examining every working drawing of such structures as this, and allowing no drawing to be used which is not authenticated by their signature. We do not now recollect all
the titults of these condemned courses ; and since the death of Mr. Logan, who was in possession of the plans with Mr. Rennie's signatures, we know not where these drawings can be referred to, (and reference to them is of little conse quence, except as a warning ;) but we do remember, that what struck us at the time as the grand imperfection, was the omission of the square central stone with dovetails, to which the timr stones next in order were attached, and also joggled by stone to the end joints, thus making the five one mass of stone, to which the whole of the surrounding stones were attached. In place of this central stone, which was of course the key and fastening of the whole, there was substituted in the drawings, a plain hexagon or octagon, we forget which ; by means whereof' the whole bonding of the course was loosened, and, had water percolated into it, it would have been destroyed by the hydrostatical pressure. An accident of this kind happened to another structure del 1 the engineer to the commissioners of the northern lighthouses had planned. and was in the course of erection upon the Carr rocks, off the east point of Fife. This structure was to be furnished with a bell, to be rung by a float ; and in order to contain the float, a hollow column was erected, having a lateral opening at the bottom. The column was, we believe, pretty well secured against the external action of the water, but it should seem that the danger of hydrostatical pressure from within had been overlooked, for, after the work had advanced so far as to be distinctly visible from the land, the sea beating over it during a violent storm, had thrown in rubbish which blocked up the lower aperture, and the hollow of the column tilled with water, which burst it into pieces, so that it vanished before it was finished. As this structure is gone, and has left no memorial, it would be of little consequence to inquire any particulars of it ; but the fact is worthy of record, as tending to show how very careful engineers should be in attending to every principle in the planning and executing marine structures ; and also how careful those who direct the building of such structures ought to be in the selection of their engineers. To suffer, in any lighthouse or beacon tower for the warning of mariners of the perils of the sea, any weak portion or point which shall endanger the stability of the structure, may be attended with more calamitous effects, at least tiu. a time, than having no lighthouse or beacon at all ; for the lighthouse or beacon gives the seaman a certain smithy, which prevents him from avoiding the danger so assiduously as he would do, were there no lighthouse there ; and, therefore, he is tempted toward the rocks ; and wrecked upon them, if the lighthouse fills before his arrival. The Bell-rock lighthouse is as secure against any casualty of this kind as a structure of human erection can be; and, front what we have stated, those who navigate the dangerous coast on which it stands cannot he too thankful to Rennie, who had the superintendence oft he building, or hold the memory of that eminent and most judicious engineer in too high estimation.