SU1SMAK1NK TUNNELING 229 



was to be built after four caissons were sunk. Then the outer 

 partition of die tirst i-aisson was t< be removed, and the ma- 

 sonry of the submarine tunnel connected with the portion of 

 the tunnel built on land. In a similar manner all the caissons 

 were to be sunk ; and when the last one was placed, and the ma- 

 sonry lining constructed, and connected with the portion of 

 the tunnel built on the other shore of the river, the partition 

 walls were to be battered down, and the submarine tunnel com- 

 pletely constructed and open to traffic. 



