n i - ■■ a ttmnnr ■Kt i . mi V i im i nn « ■■ » i ; j-»aa^iiMfiM 



inyiaiJuL . HpBiiii 



WPP*SPW»^fcl^^»W9Pi^!^lW 



Figure 23. — Vertical section through Brinel's shield. The long lever, x, supported the wood centering 

 for turning the masonry arches of the lining. (Law, .1 M<?i,<>ii oj tin Thames Tunnel.) 



PAPER 41: TUNNEL ENGINEERING— A MUSEUM TREATMENT 



223 



