When the drill-holes had been sunk to the required depth, the machine was moved back, and some plank doors were closed in front of it to prevent injury by the flying fragments of rock. Just as we reached the end of the heading the noise ceased, and the machine was drawn back, preparatory to blasting. The holes were cleared, and then three men came forward with the charges of nitro-glycerine in long tin tubes. These were put in the holes, the wires were fastened in their places, and then the men moved back; it is hardly necessary to say that I moved back at the same time, and quite as far as the workmen. Everything being ready, the signal was given.
“Look out that you are not blown down!” said my guide.
I did look out. There came a sound and a quick explosion, followed by the rumbling and crashing of the rock, and then a rush of air and smoke that almost threw me over.
The pressure of the air in the iron pipe for working the drills and ventilating the tunnel was about six atmospheres, or ninety pounds to the square inch. As soon as the blast was made, the air was turned on; the smoke from the blast was driven back, and the miners found themselves in a clear atmosphere.
After this blast it was intimated that there was nothing more to see, and we made our way out of the tunnel into the open air again, and back to the Wilson House.
On December 12th, 1872, the east heading was connected with the one driven east from the central shaft. The west heading was connected with the one driven west from the shaft on the 27th of November, 1873. This proved a splendid engineering feat.
The road bed was finished and the track laid early in 1875, and the first freight train passed through on the 5th of April of that year. The first passenger train was run through, July 8th, 1875.
ACCIDENT AT THE CENTRAL SHAFT.
Owing to the explosive action of nitro-glycerine the rock was broken for some distance beyond the limits planned in constructing the sides and arch of the tunnel, and there was constant danger of pieces of rock falling upon the track. The plan of arching it with brick was conceived of, and a contract was made in 1874, to do the arching and also to enlarge a portion of the tunnel at the eastern terminus. This work was completed, and the road is now in complete running order.
The cost of the work in the aggregate is nearly $15,000,000. The construction of the tunnel opens direct communication between Boston and Troy, and is of inestimable advantage to Massachusetts from a commercial point of view.