454 THE MENAI BRIDGE. PART VTIT. 



tween each tunnel, but at the bottom they were all 

 united by a connecting horizontal avenue or cavern, 

 sufficiently capacious to enable the workmen to fix the 

 strong iron frames, composed principally of thick flat 

 cast iron plates, which were engrafted deeply into the 

 rock, and strongly bound together by the iron work 

 passing along the horizontal avenue ; so that, if the 

 iron held, the chains could only yield by tearing up the 

 whole mass of solid rock under which they were thus 

 firmly bound. 



A similar method of anchoring the main chains was 

 adopted on the Caernarvonshire side. A thick bank 

 of earth had there to be cut through, and a solid 

 mass of masonry built in its place, the rock being 

 situated at a greater distance from the main pier; thus 

 involving a greater length of suspending chain, and a 

 disproportion in the catenary or chord line on that side 

 of the bridge. The excavation and masonry thus ren- 

 dered necessary proved a work of vast labour, and its 

 execution occupied a considerable time ; but by the 

 beginning of the year 1825 the suspension pyramids, 

 the land piers and arches, and the rock tunnels, had all 

 been completed, and the main chains firmly secured in 

 them ; the work being sufficiently advanced to enable 

 the suspending of the chains to be proceeded with. This 

 was by far the most difficult and anxious part of the 

 undertaking. 



With the same careful forethought and provision for 

 every contingency which had distinguished the engi- 

 neer's procedure in the course of the work, he had 

 made frequent experiments to ascertain the actual 

 power which would be required to raise the main chains 

 to their proper curvature. A valley lay convenient 

 for the purpose, a little to the west of the bridge on 

 the Anglesea side. Fifty-seven of the intended ver- 

 tical suspending rods, each nearly ten feet long and 

 an inch square, having been fastened together, a piece 



