THE SEVERN TUNNEL. 



79 



been the least leaky, and this ring having the support of 

 those above it was able to bear the pressure. 



As may bo supposed, there were places in the arch and 

 side wall which also flushed off under the pressure. After 

 full consideration it was finally decided to pump all the 

 water, including that from the big spring, and in conse- 

 quence of this decision, a new shaft to contain six very large 

 pumps had to be sunk at Sudbrook ; and the opening of the 

 railway had to be delayed a year or more in order to get 

 this, with the necessary machinery, boilers, and buildings, 

 all erected. 



It may here be mentioned that the writer advocated the 

 vertical bond instead of ring- work in the arches ; and, in 

 consideration of his views on the subject, a special provision 

 was made in the specification to the contract that this bond 

 should be used if ordered by the engineer-in-cliiof. He, 

 however, objected to the use of special bricks, which would 

 have been necessary to make the bonded work, and so none 

 were used. It is impossible to say what amount of leakage 

 might have taken place through the bonded work, had the 

 Tunnel been so constructed ; but it could not have been hlown 

 like the ring-work. The writer should add that he did not 

 foresee that in ring-work under great water-pressure the 

 rings would be blown one after the other, as they actually 

 were ; for he had never seen such a thing. He merely knew 

 that an arch so built was immensely stronger in every way 

 than a ring arch — much as a well-bonded house wall is 

 stronger than one would be if built entirely of stretchers, 

 like so many 4| inch walls placed one against the other 

 without being bonded together. 



The Severn water did get into the Tunnel in two places 

 near the English shore. The new red strata, which are so 

 hard under the central parts of the river are there much 



