SUBMARINE TfNNKUM; 



24i) 



and rings were provided with double (exterior and interior) 

 flanges, by means of which they were bolted together. The 

 soil behind the lining was filled with liquid cement injected 

 through small holes by 

 means of a hand pump. 

 The remarkable suc- 

 cess of the London Tower 

 tunnel encouraged 

 Barlow to form in 1871 a 

 company to tunnel the 



Thames between South- Fl - 128 - Shield Suggested by Greathead for the 



Proposed North and South Woolwich Subway. 



wark and the City, and 



Greathead, in 1876, to project a tunnel under the same water- 

 way known as the North and South Woolwich Subway. Bar- 

 low's concession was abrogated by Parliament in 1873, without 



any work having been 

 done. Greathead pro- 

 gressed far enough with 

 his enterprise to const nut 

 a shield and a large 

 amount of the iron lining 

 when the contractors 

 abandoned the work. 

 From the brief descrij)- 

 tion of his shield <riven 

 by Greathead to the Lon- 

 don Society of Civil Kn- 

 gineers, it contained sev- 

 eral important differences 

 from the shield built by 

 him for the London 

 Tower tunnel, as is shown 

 by Fip. 1 2"). The changes 

 which deserve particular notice are the great extension of the 

 shield behind the diaphragm, the curved form of the diaphragm. 



FlO. 120 Bench'* Bhli-ld fnwl on Broadway 

 I'liciitnatlc Hallway Tunnel. 



