Fig. 3. is an enlarged view of one of the agitable burners a, with its reflector b, which last measures four inches over the lips, and is raised to the parabolic curve of three inches focus; c the socket, d the section of the moveable chandelier in its groove, answerable to letters k and l, Fig. 1., and f and e Fig. 2. In reference to Fig. 3., e e is a section of part of the central cylinder of the lantern and mast of the ship.
Fig. 4. represents one of the Mushroom-Anchors, constructed wholly of cast-iron, used for mooring the Floating-Light and other craft off the Bell Rock, to which part of the mooring-chain is attached. This diagram seems so obvious as to require no particular description. Towards the head a a the shank is strengthened by means of four feathers or brackets raised upon it, somewhat resembling the connecting gills of the vegetable mushroom. These anchors weighed from 14 to 21 cwt.
Figs. 5. to 9.—Quarry Tools.—Fig. 5. is a common stone-pick, weighing from 8 to 10 lb., shown with and without the handle, which measured about 2 feet in length, but is here shortened. Fig. 6. is the Aberdeen or granite pick, weighing from 6 to 16 lb. Fig. 7. is a quarry hammer, weighing from 6 to 8 lb. used for jumping or boring batt-holes in the Rock, and the trenail-holes in the courses of the building. Fig. 8. represents the boring-irons for the trenail-holes, measuring 1¾ inches in breadth at the cutting end, and varying in length according to the depth of the respective holes. Fig. 9. is the scraper used for cleaning the holes; the perforated end being applied with a piece of rag for drying up the moisture.
Fig. 10. represents one of the oaken trenails used for keeping the stones in their places while the building was within the ordinary range of the sea. The positions of these trenails may be traced in the small circular holes of the courses, in Plate XIII. Their lower ends were cut with a saw-draught as at letter a, into which a small wedge marked b was inserted, and the trenail having been driven home, the small wedge had the effect of tightening or fixing it. The upper end c was then cut off flush with the upper bed of the stone, when it was split, and another small wedge, marked d, driven into the chisel-mark, which completed the operation of fixing the trenails into their places.
Fig. 11. represents a pair of the oaken wedges inserted into corresponding grooves cut into the perpendicular joints of the stones in each course of the solid or lower part of the Light-house, as may be traced in the small oblong holes, marked in the joints of the courses in [Plate XIII.] These wedges were chiefly intended for bringing the dove-tailed parts of the stones to a general bearing. The thick end of the wedge marked a being dropped into its groove, the smaller end of the corresponding wedge b was then inserted, and driven home till some degree of tension or firmness was obtained. This operation of trenailing and wedging was followed from Mr Smeaton’s practice at the Edystone Light-house.
Fig. 12. is a section of one of the cast-iron mortar-tubs, with its pestle, shod or loaded with a piece of malleable iron.
Figs. 13. to 15.—Cast-Iron Plate-railway.—Fig. 13. is a longitudinal view of one length of the cast-iron railways erected upon the Rock; a a a a represent the stools or upright supports, b b are the tracks of the roadway, c c one of the side stays or braces. Fig. 14. is a cross section on the line A B of Fig. 15, in which a a is the support with its cross-brace f, bolted at g g g g; b b are the railway tracks, c c c c the stays, with their connecting bolts on each side, d d the sleeper or horizontal brace connecting the top of the stools, and forming a chair or seat for the rails and grated roadway; e e e e represent the batts and spear-bolts, with which the whole was connected to the Rock, by the process of wedging with timber and iron. Fig. 15. is a plan of the finished railway; a a a a are the feet of the stools, b b the side rails or waggon-tracks, c c the stays or side braces, d d the sleepers, and h h the grated footpath. The weight of a yard in length of the railways complete, of the height of four feet, as represented in these diagrams, may be estimated about 5 cwt.
Fig. 16. represents a plan of one of the railway waggons; a is the iron handle made to hook upon either end of the waggon, so as to prevent the necessity of turning it; b b is the body of the waggon, consisting of two pieces of oak timber, bolted upon the upper part of the double frame intended for accommodating the wheels to the circular track of the railway round the building. The upper and under frames are connected with the bolt c c, so as to admit of the movement above alluded to. For the same reason, a joint was formed in the perch or middle of the frame at d. The trucks or wheels e e e e were of cast-iron, measuring 15 inches in diameter. These waggons were always left upon the Rock, being simply turned upside down, or off their wheels, in a particular part, and were seldom moved by the sea, as they weighed about 2 cwt. each.
Fig. 17. The ten diagrams, marked a, b, c, d, e, f, g, h, i, and k, are a set of moulds for one course of the solid part of the building, by which the stones were cut and prepared in the work-yard previous to their being shipped for the Rock. The application and connection of these diagrams will be better understood by examining the courses of the building in [Plate XIII.]