Whilst in Canada at this time the plot to assassinate was fully decided upon, as will be shown by the "Selby letter" subjoined. This letter was picked up in a street car in New York by a couple of ladies, one of whom, Mrs. Mary Hudspeth, testified before the Commission as follows: "In November last, after the presidential election, and on the day that General Butler left New York, as I was riding on the Third Avenue cars in New York City, I overheard a conversation of two men. They were talking most earnestly. One of them said he would leave for Washington day after to-morrow. The other was going to Newburg or New Berne that night. One of the two was a young man with false whiskers. This I observed when a jolt of the car pushed his hat forward and at the same time pushed his whiskers, by which I observed that the front face was darker than it was under the whiskers. Judging by his conversation, he was a young man of education. The other, whose name was Johnson, was not. I noticed that the hand of the younger man was very beautiful, and showed that he had led a life of ease and not of labor. "They exchanged letters whilst in the car. When the one who had the false whiskers put back the letters in his pocket, I saw a pistol in his belt. I overheard the younger one say that he would leave for Washington the day after to-morrow. The other was very angry because it had not fallen on him to go to Washington. Both left the cars before I did. After they had left, my daughter, who was with me, picked up a letter which was lying on the floor of the car, immediately under where they sat, and gave it to me, and I, thinking it was mine, as I had letters of my own to post at the Nassau Street Post-office, took it without noticing that it was not one of my own. When I got to the brokers, where I was going with some gold, I noticed an envelope with two letters in it. These are the letters, and both were contained in one envelope. After I examined the letters and found their character, I took them first to General Scott, who asked me to read them to him. He said he thought they were of great importance, and asked me to take them to General Dix. I did so. The letters are as follows:--