In the execution of this great work, if the son had, as compared with his father, certain advantages in his favour, he had also various disadvantages to contend with at Skerryvore from which the engineer of the Bell Rock was free. Mr. Alan Stevenson had steam power at his command, and the benefit of all the experience derived from the experiments of his predecessors in similar operations; but at the same time, the rock on which he had to work was at a greater distance from the land, and separated from it by a more dangerous passage than that of either the Bell or the Eddystone; and the geological formation of which the rock is composed, was much more difficult to work upon. The Skerryvore is distant from Tyree, the nearest inhabited island, about 11 miles; even in fine weather the intervening passage is a trying one, and in rough weather no ship can live in such a sea, studded as it is with treacherous rocks. The sandstone of the Bell Rock is worn into rugged inequalities, which favoured the operations of the engineer; but the action of the waves on the igneous formation of the Skerryvore has given it all the smoothness and slippery polish of a mass of dark coloured glass. Indeed, the foreman of the masons, on first visiting the rock, not unjustly compared the operation of ascending it to that of "climbing up the neck of a bottle." The 7th August 1838 was the first day of entire work on the rock, and with succeeding ones was spent in the erection of a temporary barrack of wood, for the men to lodge in on the rock. It was completed before the season closed; but one of the first heavy gales in November wrenched it from its holdings, and swept it into the sea, leaving nothing to mark the site but a few broken and twisted stanchions, attached to one of which was a portion of a great beam which had been shaken and rent, by dashing against the rocks, into a bundle of ribands. Thus in one night were obliterated the results of a whole season's toil, and with them, the hopes the men cherished of having a dwelling on the rock, instead of on board the brig, where they suffered intensely from the miseries of constant sickness. The excavation of the foundations occupied the whole of the summer season of 1839, from the 6th May to the 3d September. The hard, nitrified rock held out stoutly against the assaults of both iron and gunpowder; and much time was spent in hollowing out the basin in which the lighthouse was to be fixed. From the limited extent of the rock and the absence of any place of shelter, the blasting was an operation of considerable danger, as the men had no place to run to, and it had to be managed with great caution. Only a small portion of the rock could be blown up at a time, and care had to be taken to cover the part over with mats and nettings made of old rope to check the flight of the stones. The excavation of the flinty mass occupied nearly two summers.