HELL-GATE, IMPROVEMENT OF. 



ftcient size to be stable, would answer for 

 s MHO of the smaller rocks to be operated upon, 

 niiil also that they could not be easily protect- 

 ed against the collisions which were sure to 

 occur. They gave place, therefore, to the idea 

 of the steam-drilling cupola-scow, with which 

 many of the submerged reefs have been suc- 

 cessfully demolished. This apparatus consists 

 of two parts, the first a large scow, moored to 

 tbe shore, serving as a fixed platform, with u 

 well-hole through its bottom, affording pas- 

 sive tor the drills. It is built very strong, 

 with an overhang or guard to take the shock 

 of colliding craft. The other part is a hemi- 

 spherical cupola, open at top and bottom, made 

 with a powerful iron frame, covered with 

 boiler-iron. Its diameter is thirty feet. Its 

 hemispherical form is the one most favorable 

 to stability ; for the pressure of the currents, 

 being normal to its surface, passes through its 

 centre, and tends to hold it more firmly in 

 place, rather than to subvert it. When it is 

 required to move the dome, it is slung to the 

 bottom of the scow with chains by f our hoistinij- 

 engines. The dome serves as a framework for 

 holding twenty-one drill-tubes. The. drills have 

 cross-shaped cutting edges 5 inches long ; to- 

 gether with their rods, they have a length of 

 10 feet, and a weight of 600 to 700 pounds. 

 The engines raise them through a distance of 

 18 inches, and, releasing them, they fall upon 

 the rock by their own gravity. Before the 

 cupola is unslung from the scow, a diver ex- 

 plores the bottom to find the right spot for 

 sinking the caisson. The bow and aft moor- 

 ings of tha float are arranged to pull directly 

 against the tidal current at ebb and flood ; it 

 i* farther provided with side-anchors to stay it. 

 The mooring-chains are fastened to capstans, 

 with which the position of the scow can be al- 

 tered. The dome stands upon the bottom by 

 sliding legs, which are let go after it is low- 

 ered into position, and which fix themselves 

 as they strike the bottom by self-acting cams. 

 Tb.3 diver examines the rock under the dome, 

 to determine which of the drill-tubes may best 

 be employed. As absolute fixity of the plat- 

 form is not obtainable, the drill-rods are at- 

 tached to the pistons of the engines by a rope, 

 whose length is regulated by a feed-gear. The 

 nitro-glycerine, which was the principal ma- 

 terial used in these blasts, was brought to the 

 spot on a small soow, after the drilling-scow 

 had been removed fifty or a hundred yards, 

 an 1 there filled in tin cases of various lengths, 

 according to the depth of the holes, and low- 

 ered to the diver. He is guided to the first 

 hole by a cord, and finds his way to the others 

 by cords attached to the plugs. Before the 

 cartridges are lowered, they are attached to 

 the electric wire. The friction-battery and 

 the wet-battery, with underground connection, 

 which allowed of a much smaller length of 

 leading-wire, were both employed in these 

 blasts. Mr. Striedinger, the engineer in 

 charge, gave great attention to the improve- 



ment of the cartridge-caps, and wan able, in 

 every case, to procure an explosion, even 

 when the nitro-glycerine wan frozen ; tho per- 

 cussion was produced by about 25 grains of 

 fulminate. Ihe holes were drilled 6 or 8 feet 

 apart, and to a depth of about 4 feet below 

 the level to which the rock was to be broken ; 

 the charges averaged 50 or 60 pounds of nitro- 

 glycerine. When a reef has been sufficiently 

 broken up by the blasts, the fragments ure 

 dredged up and removed by Morris & Cum- 

 mings's steam-grapple. This machine has been 

 able, so far, to do its work without protection 

 against the currents ; but, should the force of 

 the water become too violent, as it is probable 

 it may in some parts of Hell-Gate, it is pro- 

 posed to shut out the currents by a network 

 of chains, with one side resting upon the bot- 

 tom, and one side buoyed up by a boat. A 

 similar chain-netting was devised for the pur- 

 pose of excluding currents from the lower part 

 of the drill-cupola, if this should ever become 

 necessary. 



The construction of the scow -drill machine 

 was commenced in July, 1869, and, after long 

 experiments upon the drills, to determine the 

 weight and size of point required, and upon 

 the explosive power of nitro-glycerine, the 

 practical work was commenced in May, 1871, 

 upon Diamond Reef, near the mouth of the 

 East River. The surface of this rock had first 

 to be dredged ; it was then drilled with holes 

 7 to 13 feet deep by 4 inches diameter at the 

 surface and 3^ inches at the bottom, and 

 blasted with 30 to 55 pounds of nitro-glycer- 

 ine charges. During the same year operations 

 were carried on in alternation upon Coentie's 

 Reef. This reef was broken up, during two 

 working-seasons, with 400 charged holes and 

 56 surface-blasts, and the consumption of 22,- 

 606 pounds of nitro-glycerine. Owing to a blun- 

 der in the title of the appropriation bill, the 

 dredging was obliged to be left over, in part, 

 until 1876. In Hell-Gate the Frying-Pan was 

 leveled in July, 1872, with 17 holes and 11 sur- 

 face-blasts. Pot Rock was commenced upon 

 August 5th. The number of blasts was 40 

 holes blasted and 60 seam and 24 surface-blasts. 

 During the labors here sixteen collisions oc- 

 curred ; two of the vessels were sunk, and 

 one of them, being driven under the scow, 

 carried away the dome, which was recovered, 

 considerably injured, in 80 feet of water. 

 Work was remitted upon these rocks until 

 stricter regulations should be enforced upon 

 pilots. Way's Reef was removed to the depth 

 of 26 feet below mean low-tide mark during 

 the latter part of 1874. The size of the rock 

 rising above that level was 235 feet length by 

 115 feet greatest width. The drill-holes were 

 262, with an average depth of 8.13 feet and an 

 aggregate depth of 2,130 feet. Thirty-five 

 hands was the average working-force employed 

 on the scow. Computations of Engim-i-r 

 Striedinger, in a report to General Newton, 

 gave the following numerical data : Average 



