Arnold got employment at Fortress Monroe, and was there at the time of the assassination; but the finding of the above letter in Booth's trunk, as also other evidence constantly turning up in the course of the investigations being made, identifying him with the conspiracy, led to his arrest on the 17th of April at Fortress Monroe. Arnold, when arrested, made a partial confession, relating the circumstances of a meeting of some of the conspirators held at the Lichau House in Washington about three weeks previous to his going to Fortress Monroe. [Illustration: SAMUEL ARNOLD.] This meeting must have occurred within two or three days after the writing of the above letter, immediately before Surratt's visit to Richmond, and was attended by Booth, Surratt, O'Laughlin, Atzerodt, Arnold, a man with the alias of Moseby, and another whose name he could not recollect. He denied that he had ever corresponded with Booth, but on being informed of the letter found in Booth's trunk he admitted that he wrote it. He also stated that Booth had letters of introduction to Dr. Mudd and Dr. Queen, but said he did not know from whom Booth got them. He claimed that an angry discussion took place at the meeting referred to. He said he told Booth then that if the thing did not take place that week he would withdraw. Booth got angry at that, and said he ought to be shot for talking in that way. He said that he replied to Booth that two could play at that game; and that he withdrew from the conspiracy at that time, and occupied his position at Fortress Monroe on the 1st of April. It is evident, I think, that as he began to contemplate the hazards of the enterprise, its dangers began to be more and more apparent to him. His heart failed him, and he was anxious for an excuse to withdraw from it, but had not the courage to peremptorily do so. This is the interpretation I put upon the above letter--of the altercation between him and Booth, and of his going to Fortress Monroe. There is also apparent in the letter a shade of disappointment and dissatisfaction in regard to pecuniary matters, implying that promised reward had been withheld by Booth. Early in September, whilst at a grain threshing, Arnold received a letter containing a fifty-dollar bill. Reading the letter and showing it with the money to a companion, he remarked that "he was flush." He handed the letter to his friend to read, but he, after trying to read a few lines, and finding that he could not understand it on account of its ambiguity, handed it back to Arnold, asking him what it meant. Arnold replied that something big would be seen in the papers one of these days. This was no doubt a retainer's fee, or in other words, an advance payment from Booth. The rather complaining tone of Arnold's letter, hinting at pecuniary embarrassment, would seem to indicate that Booth's promises of pecuniary reward had been large, whilst his fulfillment had been far from satisfactory.