On the night of November 4 only one layer of bricks separated them from the top of the vault, and it was decided to finish the work and do the robbery that night. Two hours' hard labor with "drag" and "jack-screw" sufficed to effect an opening, and Scott and Dunlap were lowered into the vault. They found three Marvin spherical safes protected by a burglar-alarm. But Dunlap was somewhat of an electrical expert, and was able to so surround the burglar-alarm with heavy boards as to render it of little or no danger. They experienced much difficulty, though, in blowing open the safes. The first one attempted yielded on the second explosion, and they secured five hundred dollars in currency and sixty thousand dollars in bonds. The next one was far more troublesome, not less than ten explosions being required to make way into it. And just as the task was at last accomplished, and they were on the point of seizing a great sum of money, there came a warning call from Conroy, who was doing sentry duty on the roof, and it was necessary to fly.
When Dunlap and Scott had been dragged out of the vault by their associates, they were found scarcely able to run. During all the twelve explosions of powder and dynamite they had never left the vault, but, crouching behind the boards that guarded the burglar-alarm, had remained within arm's length of explosions so violent that they tore apart plates of welded steel and shook the whole building. Worse than the shock of these explosions were the noxious gases generated by them, which Scott and Dunlap had to breathe. On coming out, their clothes were wringing wet with perspiration, and they were so weak that their legs tottered under them, and their comrades had to almost carry them for a time. But, nevertheless, they managed to walk thirty miles that night, to Lehigh, where they boarded a train to New York.
It was on this occasion that there was left behind in the vault the air-pump which Robert Pinkerton afterward recalled so shrewdly to Evans's disadvantage.
Coming, in his confession, to the Northampton Bank robbery, Evans said that the gang had considered making an attempt there for several months before the robbery was actually executed. For a time they had designed to rob the First National Bank, where Evans had been employed to put in new doors, but this scheme they afterward abandoned. Enjoying the fullest confidence of the Northampton Bank officers, Evans had made repeated visits to the bank and gained important information for his associates. It was through his influence that the bank directors decided to give the whole combination of the vault to the cashier, Whittelsey, who had previously been intrusted with only half of it, the remainder being given to one of the clerks.