ccxiv GENERAL SUMMARY OF SCIENTIFIC AND 



blc obstructions to the navigation of New York harbor. In con- 

 nection with this event, a brief summary of the oiDerations under- 

 taken by the national government for the improvement of New York 

 harbor may be of interest. These operations, as gleaned from a 

 trustworthy source, date from the year 1848, when Lieutenants Davis 

 and Porter, U. S. N., made an examination of the narrow channel 

 known as Hell Gate, leading from Long Island Sound to the East 

 River. The narrow channel between Long Island and Ward's Isl- 

 and was rendered very dangerous by Hallett's Point Reef, that pro- 

 jected out into the river some three hundred feet, and caused the 

 tide coming in from the Sound to be thrown over against an oppos- 

 ing rock known as the Gridiron. Besides these rocks, there were 

 the Pot Rock, the Frying-Pan Rock, and Way's Reef, wiiich were 

 blasted as long ago as 1851-1852, by exploding cans of jjowder laid 

 on their surface. From the above date nothing was done until the 

 year 1866, when Major-General John Newton was assigned the duty 

 of making an examination of the obstruction at this point, and of 

 preparing jDlans and making estimates of the cost of the works nec- 

 essary to remove them. The several plans submitted by this officer 

 involved the removal of the reef at Hallett's Point, as a prominent 

 feature, and in pursuance of these plans Congress made the first ap- 

 propriation in 1869 for what have since been known as the Hell Gate 

 improvements, assigning to General Newton the duty of carrying 

 them out. From this time forward operations were carried on with 

 more or less rapidity, and culminated, on the 24th of September, in 

 the demolition of the reef by explosion. Without rehearsing details 

 given in our last Annual Iieco7'd, we may add the following tabular 

 statement of the dimensions of the main headings, showing the ex- 

 tent of the submarine tunneling work : 



The total length of headings was 4857 feet, and of the circular 

 galleries or cross-cuts 2568 feet, making a total of 7425 feet. The 

 amount of rock excavated was 47,461 cubic yards, and the cubic 

 contents of the rock in the reef above the depth of 26 feet at mean 

 low water amounted to 51,000 cubic yards. The rock itself was an 



