Chap. XXIII.

CENTERING.

H05

The Coldstream Bridgehad a frame with a tieand a series of bracesunited; this truss sup-ported on each side aportion of the centre, orthe ribs, on which werelaid the planks for turn-ing the arch; this was de-signed by Mr. Smeaton .

The Centering used byMr. Telford at the bridgeof Cartland Crags pos-sessed considerable no-velty, and w T as well adapted for its purpose: as the piers were built, care was taken toprovide for a lodgment of the inclined timbers which were to support the second platform,on which the centre was to be constructed to carry the whole of the arch above it. The

Fig. 2345.

CENTRE OP COLDSTREAM BRIDGE.

temporary platform on which the materials werebrought, previously to lowering to their place, restedupon the centre, and by its weight assisted in steadyingthe work.

Fig. 2346. CENTRE OP CARTLAND CRAG bridge.

Centres made use of for Tunnellingdo not require to be always timberedthroughout; although as much orgreater care is necessary for their

CENTRE FOR A TUNNEL.