MKTH<>I>S 



LIMV, 11 NM.L> 



discussing the methods of relining timber-liiied tunnels with 

 masonry are typical examples. 



Iron Lining. The use of iron lining for tunnels was intro- 

 duced lirst mi a large scale by Mr. Peter William Barlow in 

 1869, for the set-mid tunnel under the River Thames at 

 London, England, and it has greatly extended since that time. 

 The lining of the second Thames tunnel consisted of cylindrical 

 cast-iron rings X ft. in diameter, the abutting edges of the 

 xiu-.vssive rings being flanged and provided with holes for 

 bolt fastenings. Kadi ring uas made up of four segments, 



Cross Section. Longitudino\ Section. 



Km. 44. A Typical Form <>f Tlmbnr Lining for TuiiMls. 



thrve of which were longer than quadrants, and one much 

 smaller form ing the " kry-stonc " or (-losing piece. These 

 M-gini-nts were connected to each other by flanges ami lolU. 

 To makr the joints tight, strips of pirn- or ccim-nt and hemp 

 yarn \\rre insert'd U-tut-en the flanges. Sinn- the ronstrnc. 

 ti"ii of the second Thaim s tunnel, iron lining has ln-en cm- 



'1 for a great many siilmmrinc tunnels in Knglam'. 

 Continental Kun>p*-, and Ani'-i f them having n 



n over 28 ft in diameter. Where circular iron lining is 

 employed, the Wtm part of the section is leveled up witli 

 concrete or brick masonry to carry the tracks, and the whole 



