Hallett’s Point is the most dangerous obstruction in Hellgate. From shore to shore the distance is about six hundred feet; the reef extends more than three hundred feet from one shore, so that the actual width of the channel is reduced to three hundred feet.

The water boils furiously over this reef, and turns a large part of the tide upon the Gridiron Rock, frequently throwing ships upon it. The process of drilling and blasting was considered too slow and ineffectual, and it was proposed to remove the rock by sinking a shaft upon the shore, undermining the entire reef, leaving pillars to support the rock until the work of undermining was all completed, when, by a single explosion, these pillars could be blown away, the whole reef would fall, and the dangerous obstructions to the commerce of New York would be removed.

One pleasant day, in 1871, I was one of a party to visit the scene of General Newton’s operations. Our party embarked on a small steamer at the Barge Office, and proceeded up the East River, stopping on the way to examine the operations in progress for the removal of what is known as Coenties’ Reef. This reef is about six hundred feet from Pier No. 8, on the East River, and lies directly in the busiest part of the harbor of New York, almost in the track of the ferry boats between New York and Brooklyn, and has always been considered very troublesome and dangerous. Attempts have been made at various times to remove this reef, but none of them were successful until the plan of General Newton was tried. The reef is about 250 feet long, and is 130 feet wide in its broadest part. We found a large scow anchored above the reef, and were politely taken on board. The scow is very broad and heavy, and is firmly anchored, so that ships or steamers that run against it can be very little damaged.

In two or three instances, vessels that have come in collision with the scow have retired considerably damaged, while the large and unwieldy craft, remains unharmed.

As we went on board we were taken to the centre of the scow, where there was a circular well about thirty feet across; and in this well there was a dome, which could be raised and lowered by means of machinery. At the top of the dome there was a “telescope,” twelve feet in diameter, that could be extended or shortened in order to accommodate itself to the condition of the tide. The plan of working was to anchor the scow over the place where the rock was to be drilled, and then to lower the dome until it touched the rock. As soon as one part of it struck the rock, rods were pushed out from the side of the dome to rest upon the reef, and perform the work of feet: they readily adapted themselves to the inequalities of the rock, and as soon as they were fastened in their place the dome was almost immovable.

DRILLING UNDER WATER.

Inside the dome there were places for lowering drills, and working them, by means of machinery. The drilling engines were run by steam, and the drills, nine in number, were operated simultaneously; the nine holes that they made were in a circle of about twenty feet in diameter. The drill penetrated the rock from six inches to two feet an hour, according to its hardness. When a round of holes was made, the scow was hauled off, the holes were filled with charges of nitro-glycerine in tin cans, and everything was made ready for a blast.

The work of blasting has to be done very rapidly, for the reason that a diver can only go down to arrange the charges at the period of slack water. Everything is made ready at the turn of the tide, and the very instant that the tide falls the holes are charged.

We were not in time to witness a blast; and on two other occasions, when I went to see an explosion, the performance did not come off; some slight accident had happened, so that the slack water period had passed before everything was ready.

When the round of holes has been charged, the diver goes down. The pump to supply him with air is kept at work; the charges are lowered into the water one after the other, and placed in the holes where they belong. When he has arranged everything, he gives a signal and is drawn above. The boats then back away from the reef sufficiently far to be out of the way of the explosion.