48 ANNUAL OF SCIENTIFIC DISCOVERT. 



EAST BOSTON TUNNEL. 



Mr. Clemens Herschel made a communication to the Massachu- 

 setts Institute of Technology, illustrated by models, on a mothod 

 of building subaqueous tunnels. The subject was interesting at the 

 present time on account of the advantages derivable from a direct 

 communication of some sort between Boston and East Bogton. 

 The great objection that has heretofore been constantly brought 

 up against tunnels under rivers is the supposed extreme difficuhy 

 and cost of their construction. The cause of this general opinion 

 is traceable to the difficulties encountered in building the Thames 

 Tunnel. 



It was shown how in that case the work was done under con- 

 stant danger of the water breal^ing in ; how the water did break 

 in a number of times, and how the bed of the river was then arti- 

 ficially restored by filling in with bags of clay, thiough whicJ^i the 

 tunnel was afterwards carried, — operations necessarily very costly. 

 By the proposed method there is no tunnelling, properly so called, 

 to be done. The water above and in front of the tunnel is got 

 rid of by means of an iron cofter-dam, and the tunnel is built 

 hi sections or lengths of about 100 feet 'at a time, inside the 

 cofi'er-dam, open to the sky, making little more work, after the 

 colFer-dam is in place and the water pumped out, than it would be 

 to dig a cellar and arch it over. The cotfer-dam is sunk by dig- 

 ging out the earth immediately under its walls ; the walls are 

 double and the space between is divided into chambers, each one 

 of which is accessible from above, and in which any labor can be 

 performed that has already been done in such compartments, 

 when used for making the foundation for bridge piers, by the 

 known pneumatic methods. 



At a recent hearing before the Harbor Committee of Boston, at 

 which the State Harbor Commissioners and many engineers were 

 present, it was generally acknowledged that the old objections of 

 excessive cost and difficulty were not valid against the method 

 proposed in this communication. 



The objection often made, that tunnels are too disagreeable for 

 foot travel, does not hold good on examination. Judging by 

 railroad tunnels, it is inferred that all tunnels are necessarily dark, 

 damp, and unpleasant places, whereas, by ordinary efforts, they 

 may be made pleasant. The advantages of a tunnel over a bridge 

 are, that it offers absolutely no impediment to navigation, and re- 

 quires less cost to maintain it. By making the descent on this, 

 and the ascent on the other side, with no steeper grade than 3i 

 in 100, a common grade as found in the streets, we should have 

 for a tunnel between Boston and East Boston about 550 feet of 

 open cut, and 1,000 feet of tunnel under ground on each side, 

 and 1,500 feet under the river. The estimated cost of such a 

 tunnel, to be built by this method, is $1,337,G<S5. 



The greatest depth in this channel at low water would be 32 feet, 

 and about 40 feet at high water. The bed of the channel is a firm 

 chi}", and very favorable for the Inilldiug of such a tunnel from 



