However it may have been, thinking that he had discovered me, I stepped boldly up to the "general delivery," and inquired for a letter for "Robert Marshall, railroad contractor," taking occasion to observe him closely as he was engaged in running over the letters. He seemed confused, his hands shook a little, his face was flushed, and his voice Was inclined to tremble, as he replied that there was "nothing for Robert Marshall." I attributed all this to fear lest his previous movements might have been observed, and left the office, strongly suspecting that Thomas L. was the author of the depredations in question. A few experiments in the way of "decoy letters," mailed so as to pass through that office, soon converted suspicion into certainty. One of these letters, containing sundry bank-notes, disappeared, and one of the notes was traced directly back to his hands. How this was done, the reader will probably insist upon knowing, and it is my intention to gratify this thirst for information, although in so doing I shall be compelled to reveal a degree of unskilfulness in the game of ten-pins which would deter the most sanguine gamester from betting on my head. In the basement of the hotel was a bowling saloon, which, as I had ascertained, the suspected clerk was in the habit of visiting in the evening, after closing the post-office, and this fact suggested my plan. I might have arrested and searched him at once, but I thought it the better way to watch the money exchanged by him, in the hope that some of the missing bills might thus come to light. For if he should chance to have none of these about his person, a search would spoil all, by putting him on his guard, whereas if he should offer none of them, no harm would be done, and things would remain _in statu quo_. With these views I made a confidant of the landlord of the hotel which contained the bowling saloon, and agreed to meet him there early in the evening for a "roll," and arranged that in case the young man came in as usual, my partner should excuse himself, and substitute L. in his place, to oblige a stranger, who, of course, was rolling merely for exercise. My design in making this arrangement was to fasten the expense of the evening's recreation upon L. by a brilliant and overpowering display of my skill in bowling, calculating that he would probably pass some of the stolen money in payment. This was my programme--how it was executed I shall proceed to show. "Mine host" and I had been rolling perhaps half an hour, when a fine-looking, well-dressed young man entered the saloon, whom I at once recognised as L. The landlord and myself happened to be the only ones then engaged in playing, as it was rather early in the evening for the appearance of most of those who resorted there; so L. watched our game for a while, till the landlord, looking at his watch, remarked that he had an engagement which must be attended to immediately, and turning to L., said,