Pl. XIII.
As the ground or imperfect course of the building could not be ascertained till towards the second year’s work, when the site of the Light-house was excavated, this course is represented in [Plate XV.]
Fig. 1. Plate XIII., is the first entire course, which measures 42 feet in diameter. The dove-tailed method of connecting the solid part of the Light-house here delineated, extends to the height of the entrance-door, as will be further understood by examining the section in [Plate XVI.] The outward stones of this course are of a lighter shade, being intended to represent the granite blocks, while the central part of a darker shade, represents the sandstone. The thirteen small square or cubical stones in the Plan of this course, shew the upper sides of the joggles, sunk half into the one course, and penetrating half into the superincumbent one, acting as so many steady-pins, calculated to guard against any force tending to affect the fabric horizontally. By tracing the bounding-lines of the stones, from the centre to the circumference, it will be observed, that the whole are connected by means of a system of attachments technically termed Dove-tailing, by which the stones may be said to hook laterally into one another, forming a vertical bond of connection; but it is on the gravity of the materials that the chief dependence is placed for the stability of the fabric. The small circular dots, of which there are four in the centre-stone, and two in each of the others, shew the position of the oaken trenails, measuring 1¾ inch in diameter, and varying in length from 16 to 26 inches, so as to pass through the upper or last laid course, and penetrate 6 inches into the course immediately below. Besides these circular holes, others of an oblong form were cut in the joints, as will also be observed from the Figure. These last were for the reception of wooden wedges, driven in pairs perpendicularly into the joints of the stones, with a view to bring the dove-tailed parts to a uniform bearing, before the joints were grouted with mortar; the bond throughout the building being carefully preserved, by placing the perpendicular joints over the middle of the stones immediately below, being what is technically termed “Breaking-band,”—a system universally attended to in good masonry.
Fig. 2. represents the upper side of the 27th course, or first of the Stair-case, which measures 6 feet 4 inches in diameter within walls, and 19 feet 8 inches over walls. This course is elevated 32 feet 8 inches above the Rock at the foundation of the first stone, as will be seen in the section of [Plate XVI.] Here the granite casing is discontinued, and sandstone only is in future used. It will be observed, that the same system of dove-tailing is attended to in the stair-case as in the solid: this unavoidably occasioned the working of the stones into very awkward forms, and required the utmost precaution in landing them on the Rock with safety.
The parts of this course which are not shaded, shew the plan of the entrance-door, passage, and circular void of the stair, crossed by the radiating lines of the steps, as also the form of some of the stones of the top of the solid. a a represent the base of a column of cast-iron, which renders the drop-hole for the machinery continuous from the floor of the oil-store down to the level of the passage, and so through the centre of the solid, as shewn in the section [Plate XVI.]; b is a small stove placed in the stair-case; c is the position of the Inner door, of brass, as shewn in Fig. 2. [Plate XIX.], the upper part of which is glazed with plate-glass, to preserve the light of the stair-case; d is the position of the entrance-door, which is fashioned agreeably to the circular form of the building, and is strongly bound with the brass-hinges, as also shewn in Figs. 1. and 2. of [Plate XIX.]
Fig. 3. is the 39th course of the building, and first of the provision-store, and is 45 feet 11 inches above the foundation. This apartment measures 11 feet 9 inches in diameter within walls, and 18 feet over walls. From the floor to the roof the height is 8 feet 7 inches. Here the dove-tailed system, excepting at the end joints, and in the centre stones of the floors, was laid aside. At this level another system of connecting the courses was adopted, by means of a zone or belt, which was raised or worked upon the upper bed of the stones, and fitted to a corresponding groove in the course laid immediately above, as may be seen by tracing the diagrams representing the habitable parts of the house. This zone or belt, together with the horizontal plan of the floors, form the chief distinctive differences between the Designs of the Edystone and Bell Rock.
Fig. 3. The parts in this Figure which are not shaded represent the two windows of this apartment with the landing at the top of the stone stair-case. a a represent the storm-shutters, which will be more fully seen in [Plate XIX.] b b are the outer glazed windows; c c the inner glazed windows; d the open trap-ladder, with its brass hand-rail, leading to the light-room-store; e e the cast-iron coal magazine; f f f f the water-cisterns, of cast-iron, lined with a mixture of pitch and sand, and containing each 150 gallons; g g g g the four cast-iron magazines, for containing the provision casks, and various implements; h h the machinery, placed on a level with the top of the water-cisterns, for raising the stores from the entrance-door of the building to the Light-house; i i is the hole perforated through the wall for the passage of the chain for lifting the stores, the operation of which will be better understood by examining [Plate XVI.]; k the cast-iron stage upon which the light-keepers stand when they work the machinery for taking up the stores; l l the cast-iron steps leading to the stage k.
Fig. 4. is a plan of the floor of the light-room store, being the 48th course, which is 55 feet 10 inches above the foundation. This apartment, within walls, measures 11 feet 10 inches, over walls 16 feet 10 inches, and its height is 8 feet 7 inches. The shaded part of the floor marked a a a a a a a, represents the copper oil-cisterns, coated with tin, calculated to contain one whole year’s stock of oil, or about 1100 gallons. This apartment being chiefly occupied with these cisterns, there is only one window in it; b is the trap-ladder, and shews also the manhole, measuring 3 feet in its greatest length and 2 feet in breadth; c the store-room door; d d the position of the oaken pannelled partitions, which separate and inclose the store-room from the stair.
Fig. 5. being the kitchen floor, forms the 57th course, which is elevated 65 feet 8 inches above the foundation. This apartment measures 11 feet 11 inches in diameter, over all 16 feet, and its walls are 8 feet 9 inches in height. This room, in the position of its windows, manhole, and trap-ladder, is similar to what has already been described in reference to Figs. 3. and 4. In Fig. 5, a is the door leading to the apartment below; b the door leading to the trap-ladder of the apartment above; c c the oaken partitions, formed into lockers, which shut off the stair from the apartment; d is the cast-iron kitchen range or fire-place, which stands free and unconnected with the walls, forming a connected piece of pannelled work, extending from the floor to the ceiling; e is a strong cast-iron fender, and also a receptacle for the ashes; f f copper coal-boxes, formed into seats, on each side of the fire-place; g the cook’s table and locker; h the handle of the pump, by which water is raised from the provision-store or the second floor below; i i other lockers, also formed into seats.