984 Transactions of the American Institute. 



day is about 900,000,000 tons, a fact wliicli effectually dispels all 

 question as to the sanitary effect of such a causeway. 



Names. Supply. 



Harbor and Newark bay 190 > 000 , 000 



Hudson river ' 400,000,000 



East river and sound 180,000,000 



830,000,000 

 Sound loss 140,000,000 



690,000,000 



At the conclusion of Mr. McElroy's paper, Mr. Emery made some 

 remarks as to the great value of the paper just read and the sta- 

 tistics embraced in it. 



The discussion as to improving IN'ew York harbor, and the influ- 

 ence of bridges across the East river, was continued until a late hour, 

 when the association adjourned. 



February 25th, 1869. 



Professor S. D. Tillman in the cliair ; Mr. C. E. Emert, Secretary. 

 The Tunnel at Chicago. 

 Mr. Thomas D. Stetson gave a detailed description of the Chicago 

 tunnel. The Thames tunnel, he said, was not quite a success, on 

 account of the poor way for carriages to get into it. There is a place 

 for foot passengers, but none for carriages. The Chicago tunnel is 

 the only large one under a river where carriages can cross with ease. 

 The water i'fe fourteen feet deep from the lowest water line, and the 

 w^dth of the river is 200 feet. The top of the tunnel is on a level 

 with the river. After the brick work was finished, it was proposed 

 to cover it with lead, but it was covered with mastic and cement, the 

 refuse of petroleum, and other things, some live-eighths of an inch 

 thick. Over that was placed masses of concrete; then this was cov- 

 ered with flag stones. This Chicago tunnel is the only one in 

 America which is a success. It is designed to have it well ventilated. 

 There is a strong current of air through it. The grade is one in six- 

 teen feet, about the same as that at the Brooklyn side of the Wall 

 rstreet ferry. The width of the arches is thirteen feet ; the foot way 

 IB about nine feet^ ajid the carriage way ten feet. It is lighted by 



