The building operations in 1840 were entirely carried on by means of two cranes with moveable jibs, of which one was fixed just beyond the foundation, at the place shewn in [Plate III.], between the landing quay and the Tower, and was chiefly used in bringing forward the materials; and the other, placed in the centre of the Tower, served for laying the stones, and was raised along with the rise of the building. So perfectly had the stones been dressed in the workyard at Tyree, that no alteration or paring of the beds or joints was required; and such was the facility afforded by the building apparatus, that by working 14 hours, we occasionally set, through the activity of Mr Charles Stewart, the foreman builder, so many as 85 blocks in a day. The first course of masonry was laid by means of a wooden trainer; but the place of all the subsequent stones was, as already noticed, regulated by the use of plumb-templets, whose inner faces were arcs of the generating hyperbola. By those means we succeeded in setting, in a most perfect manner, six courses, which carried the building to the height of 8 feet 2 inches, and contained a mass equal to 10,780 cubic feet. That quantity is not greatly less than the whole materials of the Eddystone Lighthouse Tower, which, according to my computations from the drawings of Smeaton, do not exceed 13,300 cubic feet, and is somewhat more than one-third of the contents of the Bell Rock Tower, which are about 28,500 cubic feet. That frustum was also nearly equal to one-fifth part of the whole mass of the proposed building, which is about 56,000 cubic feet. Of the six courses, the first three are of Hynish gneiss, and the rest are of granite from the Ross of Mull. The comparative merits of those two materials may be stated as follows:—The Hynish stone is harder, and susceptible of finer workmanship, and perhaps its most perfect blocks are more durable; but it requires much more labour in dressing than the Mull granite, which is more homogeneous in its structure and is not intersected by hard veins, like those which occur in the gneiss of Tyree. There is good reason also for concluding that the Mull stone is sufficiently durable, because it contains but a small proportion of micaceous matter, and in its texture closely resembles some of the blocks of St Oran’s chapel in the neighbouring Island of Iona, which have resisted the action of the weather, it is believed, for more than 600 years and still retain the marks left by the tools of the workmen. I had also carefully compared the density of the Hynish and Mull stones, by weighing blocks of known dimensions, and found that it requires 13·16 cubic feet of the former, and 13·66 cubic feet of the latter to weigh one ton, a difference much less than the appearance of the stone would lead one to expect. A Tower of the dimensions of that at Skerryvore, built entirely of Hynish stone, would have weighed about 4308 tons, while the same mass of Mull stone would weigh 4252 tons, leaving a difference of not more than 156 tons in favour of the Hynish stone.
The mortar employed in the building was composed of equal parts of Aberdda lime and Pozzolano earth, and was therefore identical, in its composition, with that used by Smeaton at the Eddystone. Not having been able, after searching the neighbouring islands, to obtain good sand, I found it inexpedient to adopt the proportion of equal parts of lime, sand, and Pozzolano, which were so successfully used at the Bell Rock; but so perfect was the adhesion of the mortar used at the Skerryvore, that in that mass of 800 tons only two small leaks were discernible, which being ripped or opened with an iron, and allowed to run dry, were afterwards carefully repointed, and have never since shewn the slightest symptoms of leaking.
CHAPTER VII.
OPERATIONS OF 1841.
Hynish workyard. The workyard at Hynish presented a very busy scene during the summer and winter of 1840; and the desolation and misery of the surrounding hamlets of Tyree seemed to enhance the satisfaction of looking on our small colony, where about 150 souls were collected in a neat quadrangle of cleanly houses, conspicuous by their chimnies and windows amongst the hovels of the poor Hebrideans, who generally make no outlet for the smoke in their gloomy dwellings, but permit it to escape by the doors. The regular meals and comfortable lodgings and the cleanly and energetic habits of the Lowland workmen, whose days were spent in toil and their evenings, most generally, in the sober recreations of reading and singing, formed a cheering contrast to the listless, dispirited, and squalid look of the poor Celts, who have none of the comforts of civilized life and are equally ignorant of the value of time and the pleasures of activity.
The number of masons employed in 1841, varied from 60 to 84 and they were chiefly engaged in dressing blocks for the Lighthouse-Tower, in discharging the cargoes of vessels loaded with stone from Mull and also in shipping stones for the Rock, in which operation, their acquaintance with the handling of dressed materials and their readiness in working the cranes, made them very useful in directing and also in working along with the native labourers, who, partly from incapacity and partly from excessive indolence, could not be trusted for a moment to themselves. During that year, upwards of 38,000 cubic feet of granite were dressed into blocks with straight beds and joints, and with faces of double curvature, so as to suit the contour of the Tower, when arranged in the wall. The blocks were also fitted with stone joggles, for retaining them in their places, and with lewis-holes for raising them in the manner usually practised in building materials of that description. Of those materials upwards of 70 blocks were floor-stones (see Plans of 84th and 85th courses, [Plate VIII.]), dovetailed on the heads, checked on the joints and having a plain surface on the upper and a concave one on the under bed. The necessity of preserving throughout their entire joints a perfect uniformity of bearing, made the dressing of those materials a work of great nicety; and each stone, as before noticed, being cut according to moulds, was fitted temporarily in its place on the platform at Hynish, previously to its being laid aside as ready for transport to the Rock. Those various operations were conducted with great care; and the stones, which were regularly arranged and numbered according to a schedule, formed, at the time I left the workyard in the end of October, a considerable pile, bearing ample testimony to the diligence and zeal of Mr James Scott, the foreman of the workyard and leader of the party ashore.
Owing to the uncertain and stormy weather in spring, it was not till the 13th of May, that the first landing was effected on the Rock. The Rock. The result of our visit, however, was most satisfactory. We found the Barrack quite as we had last seen it six months before; and not one joint of the pile of masonry, which we had left exposed to the waves, had been shaken or started. The Railway and Landing Wharf, although much exposed to the breach of the sea, had survived the winter’s storms with no greater damage than the loss of one of the sleepers or beams, on which the rails rested, which had been torn by the waves from its fixtures to the rock. It was not till a week after our first landing that we were enabled again to take up our quarters on the Rock; for we had few landings in the mean time, and some of them, owing to the heavy surf which played round the Rock, were of no very satisfactory kind. Our first experience of this season was indeed far from inviting. So difficult was the first landing, that we were forced to direct all our endeavours to laying in a small stock of provisions in the Barrack, before being left on the Rock; and, considering the scanty nature of the supplies which the weather permitted us to secure, it was thought prudent to restrict the number of men to eight masons and myself, with as many tools as we could land, to enable them to make the necessary repairs and arrangements before fairly commencing for the season the works of a more strictly progressive character. The vessel then returned to Tyree with the rest of the men and all the heavy apparatus which we could not land; and, to add to the unpleasantness of being left in such a position, with the improbability of a visit from the vessel for several days, one of the masons took alarmingly ill soon after the steamer was too far off for a signal, and suffered so acutely during the whole night, that his piercing cries in the spasms which accompanied his disorder, combined with the howling of a strong north-wester and the incessant lash of the waves, deprived the whole party of sleep during the first night. In this uncomfortable predicament, until the steamer returned on the 22d, we spent two days exposed to winds piercingly cold and in apartments soaked with spray, which found its way through inlets which had been made by the winter’s storms. We were not sorry, at the same time, to have an opportunity of removing the poor man to the care of Dr Campbell, the surgeon who was attached to the workyard at Hynish and of reinforcing our stock of provisions and the detachment of men. We also succeeded in landing the cranes and other building apparatus, which, owing to the heavy surf on the 20th, we had not been able to accomplish.
The few first days after getting fairly established in our habitation for the season, were occupied in extending the railway to a point on the northern part of the Rock, somewhat sheltered during certain seas (see [Plate III.]), where a crane for stowing the materials previously to building them had been erected; and thus it was not till the 25th of May that the first cargo of stones was landed. Next day a crane (then thirty-four years old), which had been used in the building of the Bell Rock Lighthouse, was placed on the top of the masonry, and the more cheering operations of mixing the mortar and of setting stones were begun.
In spite of the unfavourable state of the weather and the continual distraction of our exertions, occasioned by storms and the landing of materials, we continued our operations with such vigour as to complete the solid part of the masonry of the Tower on the 8th July. Until the building had reached to the level of 15 feet, the work was carried on by the use of two jib-cranes, one on the Rock and the other on the Tower, by means of which latter the stones were set, after being brought to hand by the first. But above that level, shear-legs similar to those used at the Eddystone, were employed. Those shear-legs were about 50 feet high, and were erected in the situation, at the side of the Tower, shewn in [Plate III.] They consisted of two spars attached at the base to jointed sockets batted into the Rock, and connected at the top by means of a crosshead of timber. The jointed sockets permitted the shears to hang forward at any angle suited to the level and distance of the part of the Tower to be reached; and chain guys both in front and behind, secured them from falling either backwards or forwards. At the crosshead hung an iron sheave with a chain, one end of which was provided with a hook for raising stones, while the other was wound around the barrel of a crab machine well batted down to the rock, by working which the blocks were raised to such a level as to be within reach of the building crane on the top of the masonry. The shear-poles were used, until the building of the Tower was completed, to raise the stones the first lift of forty feet above the Rock. In the later stages of the work, the stones, instead of being taken by the building cranes directly from the shear-poles, were raised from storey to storey by means of crabs placed inside the Tower, which worked chains, reeved through sheaves hanging from the end of beams projecting from the windows. Such beams are called needles, and are described at page 504, and shewn in Plate IX., fig. 3, of my Father’s Account of the Bell Rock Lighthouse, where they were used for the same purpose.
During the early part of the season the weather was intensely cold, with showers of sleet and heavier showers of spray, which dashed round us in all directions, to the great discomfort of the poor masons, whose apartments did not admit of a large wardrobe, while they had not the benefit of much room for drying their clothes at the small coboose or cooking-stove in the Barrack. For days together, also, the men were left without building materials, owing to the impossibility of landing them, or, what was worse, without the power of building what we had on hand in consequence of the violence of the winds. During such times we often felt much anxiety about the safety of the stones which we had piled on the rock ready for being built; and it took no small trouble, by the occasional application of the crane, to save them from being swept into the sea by the surf. The Waves. Nothing struck me more than the illusive effect produced on the mind by the great waves which rolled past the rock. The rapidity of their movements, and the noise which accompanied their passage through the gullies and rents of the rugged reef, seemed to give them the appearance of being much larger than they really were; and, even when viewed from the Tower, after it had risen to the height of 30 feet, they seemed, on approaching the rock, to be on the eve of washing right over the top of the building and sweeping all before them into the sea. It was a long time before, by continually watching the waves and comparing their apparent height with the results of their impact on the rock, we were enabled to correct our notions of their magnitude, so as to mark the approach of their crested curling heads with composure; and some of the party never became sufficiently familiarized with those visitors, to avoid suddenly looking round when the rush of a breaker was heard behind them, or recoiling a few paces when they saw its towering crest apparently about to burst in a torrent over their heads. It was only after a long residence on the rock and continual experimental observation, that I acquired confidence to approach within a few feet of the point which I expected the breakers to reach. I occasionally suffered for my temerity, by being thoroughly drenched with spray; but by long perseverance, I attained considerable skill in predicting the limits of their influence, though ever and anon an extraordinary wave overthrew all our confidence, by bursting far above the boundaries which we had assigned in our minds. That, however, did not generally occur in calm weather, but after strong gales from the N.W., when the waves had assumed the larger and more flattened form known by the name of the ground-swell. To gauge the height of those waves by means of a vertical rod, graduated with large divisions, so as to be read at a little distance, as the waves washed it in passing, was an object I had long in view; but I found it utterly impossible to apply any fixture in the deep water, in a situation fitted for the purpose. By making numerous comparisons, however, of the waves, with various known points of rock near the main Rock, and by availing myself of the observations of some of the more intelligent of the masons, I was led to conclude, that the greatest elevation of an unbroken wave, measuring from the hollow to the crest, does not, in the sea around the Skerryvore, exceed 15 feet; but the sailors, perhaps from their being less accustomed to accurate measurement, generally estimated it at 30 or even 40 feet. Colours of breaking Waves. I was often much interested, while I sat watching the waves that boiled round us on every side, to observe the peculiar tints which they assumed at the moment of breaking, passing as they did from the bluish-green colour of solid water by very rapid changes, to a delicate and very evanescent blush of rose colour, which invariably accompanied their greatest state of comminution or disintegration. Those appearances I have often observed in other places, and I supposed them to be produced by reflection from the thin plates of water; and took them for indications of the perfect homogeneousness of the sea-water, in regard to density, and also of the similarity of its condition at the moment of breaking.
The Seals. Amongst the many wonders of the “great deep,” which we witnessed at the Skerryvore, not the least is the agility and power displayed by the unshapely seal. I have often seen half a dozen of those animals round the Rock, playing on the surface or riding on the crests of curling waves, come so close as to permit us to see their eyes and head, and lead us to expect that they would be thrown high and dry at the foot of the Tower; when suddenly they performed a somersault within a few feet of the Rock, and diving into the flaky and wreathing foam, disappeared and as suddenly reappeared a hundred yards off, uttering a strange low cry, as we supposed, of satisfaction at having caught a fish. At such times the surf often drove among the crevices of the Rock a bleeding cod, from whose back a seal had taken a single moderate bite, leaving the rest to some less fastidious fisher.