Chap. VIII.
5 13
arc perfectly immoveable, and, unless the entire mass of rock were to give way, would bearany stress that might be given them.
Fig. 519. SADDLES AND TIES FOR CARRYING CHAINS.
The saddles and ties which carry the main chains through the front of the Caernarvon-shire toll-house are formed of cast-iron plates; they are 3 feet 5 inches wide; the holesthrough which the chains pass are 2 feet 4 inches in width ; the four plates, with thepassage for the sixteen chains, are admirably put together, two being in the middle, andone at each extremity ; the cast-iron blocks or saddles arc 8 feet 7 inches in width acrossthe bottom, in the direction of the chains, and 7 feet in height, the spaces between thefour bars which hold the chains being each 7 inches. .These saddles were all cast withholes, in order that the tackle might be adjusted and attached by which they could behoisted. The frame for raising these castings was made of timber; the platform at bottomwas 30 feet in extent, and its total height was 74 feet; an additional timber was fixed tothe sides to a height of 26 feet; the blocks were secured by ropes to the top, and passedas shown in the figure, which represents the action of elevating a part of the iron work.At the side is a section of the frame-work, to the top of which is attached two guy-ropes.
There was also an ingenious machine or clam made use of for holding the ropes of thehoisting tackle whilst fleeting them on the capstan, and which was found of the mostessential service. The plan of the saddles shows their position; the parallelogram, uponwhich the four are placed, measures 37 feet 6 inches in length, and 14 feet in width.
The plan of the great pyramid exhibits the planking of the two carriage-ways. Themass of masonry in the middle is 6 feet in width ; the space for the traffic on each side9 feet, and the thickness of the exterior walls at the greatest 9 feet, and in the less 6 feet.The pavement, as it is laid over the planking, is partly shown in the figure. The trans-
ILtVATION.
SBCTI0N3.
I LAN
Fig. 520
METHOD OF SECURING MAIN CHAINS TO THE ROCK-
L 1