violence against the Tower, is apt to be forced through a straight or plain joint. The stones in the higher courses throughout each ring are also connected at the ends by double dovetailed joggles, which unite the two adjoining stones; and the walls are, besides, tied together at various points by means of the floor stones, which are all connected by dovetails let into large circular stones which form the centres of the floors. I also ventured to leave out the metallic ties at the cornice, which consisted, at the Eddystone, of chains, and, at the Bell Rock, of copper rings. The reasons which induced me to adopt this change I need not here enlarge upon. It is sufficient to state, that I believe I have nearly balanced the forces which would have tended to throw the cornice outwards, had a greater disproportion existed in the weight of the outer and inner parts of the cavetto, and to point out (Plate VII.) that the Lightroom or highest floor occurs, at such a level, as of itself to answer all the ends which metallic ties could have served. [16] Account of the Bell Rock Lighthouse, Plate XXI. CHAPTER IV. OPERATIONS OF 1838. ~Temporary Barrack on Rock.~ The hazardous nature of the anchorage, and the consequent difficulty of mooring a vessel in the neighbourhood of the Skerryvore Rock, induced me, from the first, to consider it as a matter of great importance, even at a large expenditure of time and money, to erect some temporary dwelling on the Rock for the accommodation of the people engaged in the work, with the view of rendering the operations less dependent on the state of the sea, which varied with every wind. So important, indeed, did this object appear to me, that I was at times apt to look upon it as an indispensable step towards ultimate success. That opinion was amply confirmed during our first season’s operations, by the experience of the oft-recurring difficulty of returning to the moorings when driven away by stress of weather, together with the daily risk and loss of time in landing the workmen in small boats, even in weather when they could be profitably occupied if once placed on this small _terra firma_. With this view, I naturally turned to the same plan which had been adopted at the Bell Rock, where the temporary barrack stood the test of five winters. That structure, which is represented in Plate No. V., and is particularly described in the Appendix to my father’s Account of the Bell Rock Lighthouse, consisted of an open framework of six logs, about 47 feet long and 13 inches square, assembled in such a manner as to form by their union a hexagonal pyramid, on the top of which rested a wooden turret; the whole erection rising to the height of about 60 feet above the rock. This pyramidal framework was strongly trussed and tied; and, being open at the lower part, offered little resistance to the waves. The upper part contained a gallery for keeping various stores and such materials as could not be safely left