Rensselaer Union, Volume 8, Number 9, Rensselaer, Jasper County, 18 November 1875 — The Great Blast. [ARTICLE]

The Great Blast.

The work of deepening and enlarging tne East River channel at Hallett’s Point is fast approaching completion, and it is now attracting the special attention of engineers and men of science throughout the country. Owing to the peculiar formation of the rock at Hallett’s Point, together with the narrowness of the present channel, and the almost uninterrupted passage of vessels, the -work has been (lone under many disadvantageous circumstances. After a tedious work of nearly six years the tusk of excavating has at last been completed, and the secondary work of preparing for the grand blast is now going on. Inasmuch as the explosive power to be used on the final blast will be about 50,000 pounds of nitroglycerine, or about eight times as much as has ever been simultaneously- discharged before, much interest and not a little anxiety is being manifested in the result. The work, which is being superintended by Mr. William H. Heuer, was begun in laOfi, and the amount expended on it has been roughly estimated at about $750,000. The excavation extends under two and a half acres of gneiss rock, vertically stratified and running jn a northeasterly and southwesterly direction. Starting from a main shaft thirty-four feet below mean low water, ten main headings sloping down to fifty-two feet below mean low water have been extended out to an average length of 550 feet each. The height of these main headings varies from eight to twenty-two, feet each, with an average width of fourteen feet. From the main headings intermediate headingshave been cut, and at uniform distances circular galleries have also been cut across the headings, thus forming a series of piers at their points of intersection. There are in all 173 piers, which form the entire support of the roof and of the water above it, and which also separate the forty-one headings and ten galleries. It is estimated that the entire amount of rock to be broken by the proposed blast will aggregate about 44,000 cubic yards. Sindh the completion of the excavation and the bringing down of the piers to an .uniform size, the work of boring holes in the roof and sides has been begun. For this .purjiose six Burleigh drills are used daily, boring about twenty-one hol'es in twenty-four hours. The working force now engaged in this work is 120 men, divided in to three gangs, each of which work eight consecutive

hours, in order that there may beno cessation. Capt. Heuer expects to complete the drilling about the last of January, when the important work of charging each hole will b$ begun. This will have to be done by experienced workmen with great care ffffd w ill probably occupy about two months. The explosives will be placed in iron tubes, each of which will have a direct battery connection besides being connected with the adjacent holes by means of a series of small tubes filled with the nitro-glycerine. This precautionary measure will be taken inasmuch as the experiment of discharging 6jOOG charges by means of one battery has never been tried, and by this system it is claimed that although the battery should fail to ignite all the charges simultaneously yet the discharge will nevertheless be instantaneous. It is expected that the blast,, which it has been proposed to have on the Fourth of July, 1876, in celebration of America’s Centennial, will entirely demolish the undermined two and a half acres of rock and break it into small pieces, which can afterward be removed by dj-edging. This will necessitate an additional outlay, as estimated by Gan. Newton in his recent annual report of the War Department, of about $450,000/or the next fiscal year. As regards the explosion of so large a quantity of nitro-glyceriheCapt. Heuer does not anticipate that there will be any great shock to the neighborhood nor that there will be the least danger attending the blast, as upon a previous occasion, when he fired a blast of42,ooopounds of powder in the San Francisco harbor, the only external visible effect was the elevation of an immense volume of water, whose transverse diameters were 200 and 250 feet, to a height of about 150 feet. Here, as will be the case in the expected explosion at Hell Gate, the water was let into the tunnel, thus operating as aJampExcavatfag is still going on at Flood Rock, although the work will be necessarily delayed until after the great blast at Hallett’s Point is over. There are at present only about ten men engaged upon the work. A shaft sixty feet deep has already-been-sunk and two tunnels, each about twenty feet long, have been excavated, the one running across toward the New York shore ana the other in the direction of Hallett’s Point. It is thought that it will take about two years to complete the •work, by which time nearly all of the obstructions will have been removed from the neighborhood of Heil Gate.—Y. Y. World.