Before the excavation for the foundation of the tower was made, a single conical loaf of rock, about five feet in diameter, rose to the height of eighteen feet above the level of high water, the greater part of the rest of its surface being about six feet above the tide mark. * * * * * In addition to its shattered and disjointed appearance, the Skerryvore Rock presents, in another respect, a striking example of the action of the sea, which no one, on first landing on the rock, can fail to perceive. I allude to the glassy smoothness of its surface, a feature that existed to so remarkable an extent as to have proved throughout the whole duration of the work, but more especially at its commencement, a serious obstacle and hindrance to the operations. It may, at first sight, appear strange that this grievance should have been so much felt; but, when I mention that the landings were often made in very bad weather, it will be obvious that there was considerable danger in springing ashore from a boat in a heavy surf upon an irregular mass of rock as smooth and slippery as ice. The workmen were, in that respect, often sorely tried, and many inconvenient accidents occurred from falls. It was after one of these trials of patience, that the foreman of the masons was heard very graphically to describe a landing on the rock as “like climbing up the side of a bottle.” Instead of a weather-beaten rock, whitened by the dung of sea-fowls, and with marine crustacea adhering to it, the surface of the Skerryvore is smoothly polished by the action of the waves, every projecting angle or point is worn down, and the whole presents more the appearance of a mass of dark-coloured glass than a reef of gneiss-rock. Excepting in some of the more sheltered crevices, no marine crustacea find shelter; but different kinds of sea-plants grow upon it, in great abundance, at and below the low water mark. These plants are, doubtless, enabled to resist the action of the waves in the same way as the sapling, yielding to the blast, is preserved during the storm that uproots the aged and more stubborn oak. * * * * * The rocks of Skerryvore have the same characteristics as those of the neighbourhood of Tyree, being what we may, perhaps, call a syenitic gneiss, as it consists of quartz, felspar, hornblende, and also mica. It will be seen, from the narrative of the progress of the works, that this rock was, from its hardness, exceedingly difficult and tedious to excavate. The only variation in the geology of the Skerryvore, is the presence of a trap rock, in the form of a dyke of basalt, which intersects the strata, and exhibits a fine specimen of the intrusion of igneous rocks. It is shewn in Plate, No. III., by a thick black line. * * * * *