For a more complete and perfect mode of making such measurements, the reader may consult Colonel Mudge’s Account of the Trigonometrical Survey of England and Wales, in two volumes quarto; a work which shows the astonishing accuracy with which that great National Survey is conducted; and also, the correctness to which mathematical instruments have been brought; and strongly illustrates the difficulties which assail man, when he aims at absolute precision, even in the most simple of the arts.
Tuesday, 14th.
Artificers return to the Bell Rock.
The Smeaton having, in the course of the last ten days, lifted such of the moorings as could now be dispensed with, took the Dickie praam-boat in tow, and sailed for Leith, to load the cast-iron sash-frames of the Light-room. On her return to Arbroath, she took on board the stone-steps for the Light-house, 23 in number, to be erected between the passage of the entrance-door and the provision store, as will be seen from the section of [Plate XVI.] With these she sailed to-day at 1 P. M., having on board 16 artificers, with Mr Peter Logan, together with a supply of provisions and necessaries; who left the harbour, pleased and happy to find themselves once more afloat in the Bell Rock service. At 7 o’clock, the Tender was made fast to her moorings, when the artificers landed on the Rock, and took possession of their old quarters in the Beacon-house, with feelings very different from those of 1807, when the works commenced.
The Smeaton is in danger, and obliged to leave her Station.
The barometer, for some days past, had been falling from 29.90, and to-day it was 29.50, with the wind at N.E., which, in the course of this day, encreased to a strong gale, accompanied with a sea which broke with great violence upon the Rock. At 12 noon, the Tender rode very heavily at her moorings, when her chain broke at about 10 fathoms from the ship’s bows. The kedge-anchor was immediately let go, to hold her till the floating-buoy and broken chain should be got on board; but while this was in operation, the hawser of the kedge was chaffed through on the rocky bottom, and parted, when the vessel was again adrift. Most fortunately, however, she cast off with her head from the Rock, and narrowly cleared it; when she sailed up the Firth of Forth, to wait the return of better weather. The artificers were thus left upon the Rock with so heavy a sea running, that it was ascertained to have risen to the height of 80 feet on the building. Under such perilous circumstances, it would be difficult to describe the feelings of those who, at this time, were cooped up in the Beacon, in so forlorn a situation, with the sea not only raging under them, but occasionally falling from a great height upon the roof of their temporary lodging, without even the attending vessel in view, to afford the least gleam of hope in the event of any accident. It is true that they had now the masonry of the Light-house to resort to, which, no doubt, lessened the actual danger of their situation. But the building was still without a roof, and the dead-lights, or storm shutters, not being yet fitted, the windows of the lower storey were stove in and broken, and, at high-water, the sea ran in considerable quantities out at the entrance-door. In the course of this afternoon, the spring-tides being now at the highest, the bridge or gangway was also for a time rendered completely impassable, from the quantity of sea that constantly washed over it. The smith’s gallery, at the same time, was also partially broken up, and several bags of coal, a barrel of small beer, and a few casks, containing pozzolano, lime and sand, were all swept off the Beacon. When the sea left the Rock, it was likewise found that two of the cast-iron legs of the sheer-crane were broken, and that some pieces of the Railways had been torn up.
Thursday, 16th.
Mortar-gallery completely broken up.
The gale continues with unabated violence to-day, and the sprays rise to a still greater height, having been carried over the masonry of the building, or about 90 feet above the level of the sea. At 4 o’clock this morning, it was breaking into the cook’s birth, when he rung the alarm-bell, and all hands turned out to attend to their personal safety. The floor of the smith’s or mortar-gallery was now completely burst up by the force of the sea, when the whole of the deals and the remaining articles upon the floor were swept away, such as the cast-iron mortar-tubs, the iron hearth of the forge, the smith’s bellows, and even his anvil, were thrown down upon the Rock. The boarding of the cook-house, or storey above the smith’s gallery, was also partly carried away, and the brick and plaster-work of the fire-place shaken and loosened. At low-water, it was found that the chain of the moveable beam-crane, at the western wharf, had been broken, which set the beam at liberty, and greatly endangered the guy-ropes by its motion. It was observed, during this gale, that the Beacon-house had a good deal of tremor; but none of that “twisting motion” occasionally felt and complained of before the additional wooden struts were set up for the security of the principal beams; but this effect had more especially disappeared ever since the attachment of the great horizontal iron-bars in connection with these supports, instead of the chain-braces, shewn in [Plate VIII.] Before the tide rose to its full height to-day, some of the artificers passed along the bridge into the Light-house, to observe the effects of the sea upon it, and they reported that they had felt a slight tremulous motion in the building, when great seas struck it in a certain direction, about high-water mark. On this occasion, the sprays were again observed to wet the balcony, and even to come over the parapet-wall into the interior of the light-room. In this state of the weather, Captain Wilson and the crew of the Floating-light were much alarmed for the safety of the artificers upon the Rock, especially when they observed, with a telescope, that the floor of the smith’s gallery had been carried away, and that the triangular cast-iron sheer-crane was broken down. It was quite impossible, however, to do any thing for their relief, until the gale should take off.
Friday, 17th.