To prepare a fit base for the reception of the column, the shelving rock was cut into six steps, which were filled up with masonry, firmly dovetailed, and pinned with oaken trenails to the living stone, so that the upper course presented a level circular surface. This part of the work was attended with the greatest difficulty; the rock being accessible only at low water, and in calm weather. The building is faced with the Cornish granite, called in the country, moorstone; a material selected on account of its durability and hardness, which bids defiance to the depredations of marine animals, which have been known to do serious injury by perforating Portland stone when placed under water. The interior is built of Portland stone, which is more easily obtained in large blocks, and is less expensive in the working. It is an instructive lesson, not only to the young engineer, but to all persons, to see the diligence which Smeaton used to ascertain what kind of stone was best fitted for his purposes, and from what materials the firmest and most lasting cement could be obtained. He well knew that in novel and great undertakings no precaution can be deemed superfluous which may contribute to success; and that it is wrong to trust implicitly to common methods, even where experience has shown them to be sufficient in common cases. For the height of twelve feet from the rock the building is solid. Every course of masonry is composed of stones firmly jointed and dovetailed into each other, and secured to the course below by _joggles_, or solid plugs of stone, which being let into both, effectually resist the lateral pressure of the waves, which tends to push off the upper from the under course. The interior, which is accessible by a moveable ladder, consists of four rooms, one over the other, surmounted by a glass lantern, in which the lights are placed. The height from the lowest point of the foundation to the floor of the lantern is seventy feet; the height of the lantern is twenty-one feet more. The building was commenced August 3, 1756, and finished October 8, 1759; and having braved uninjured the storms of seventy-three winters, is likely long to remain a monument almost as elegant, and far more useful, than the most splendid column ever raised to commemorate imperial victories. Its erection forms an era in the history of light-houses, a subject of great importance to a maritime nation. It came perfect from the mind of the artist; and has left nothing to be added or improved. After such an example no accessible rock can be considered impracticable: and in the more recent erection of a light-house on the dangerous Bell-rock, lying off the coast of Forfarshire, between the Frith of Tay and the Frith of Forth, which is built exactly in the same manner, and almost on the same model, we see the best proof of the value of an impulse, such as was given to this subject by Smeaton.