"I guess you'll look a long while, Adrian Bagot, before you find that rag. Maybe I can get even with you for running me down last night," and Jack pulled a piece of cloth from his pocket and smelled of it. "That's the evidence!" he exclaimed, as he turned down a side street. Whether it was this change, or whether it was because his ankle suddenly healed, was not in evidence, but Jack began to walk with scarcely the semblance of a halt in his step as soon as he was out of sight of the students. The lad hurried back to his room. There he spent a busy half hour, poring over some books on chemistry. He got several test tubes, and his apartment took on the appearance of a laboratory, while many strange smells filled the air. While Jack was engaged in pouring the contents of one test tube into another there came a knock at his door. "Who's there?" he called. "It's me, Sam," was the reply. "Say, Sam, excuse me, but I can't let you in," Jack answered. "I'm working on something that I can't leave. I may have a surprise for you in the morning." "All right," Sam answered. "Here's some mail, that's all. I'll shove it under the door." There was a rustling of paper and several letters came beneath the portal. Jack laid aside his test tube and gathered them up. One was from his aunts at home, another from Judge Bennetty regarding the payment of certain bills Jack had contracted, while the third was in unfamiliar handwriting. "I wonder who that's from," said Jack. "The best way to find out is to open it." He ripped the envelope down, and, as he did so, a piece of paper fluttered to the ground. Picking the missive up, Jack read: "It's a long lane that has no turns. I'll get even with you for having me suspended and sent away from the Hall. My time will come yet. "Jerry Chowden." "Jerry Chowden," murmured Jack. "So he's trying to scare me, eh? Well I guess he'll find I don't scare." Jack slowly folded the letter and placed it back in the envelope. He glanced at the postmark, and saw it was stamped "Chicago." "Wonder how he got out there," he mused. "Well, I'm glad he's far away," and he gave little more thought to the matter of the bully, a nephew of Professor Grimm's, whose vain attempt to cast disgrace on Jack, in the matter of painting a pipe on the professor's portrait, had rebounded on his own head. He had been suspended for two months for the escapade, which Jack was accused of, but which our hero managed to prove himself innocent of, and, since leaving the Hall, nothing had been heard of him. "Maybe I'll meet him if I get out west on that strange hunt of mine," thought Jack, as he went on with his chemical tests. He worked far into the night, and when he put out his light he said to himself: "I think I've got things just where I want them." CHAPTER IV A LESSON IN CHEMISTRY Jack was awakened next morning by a knock on his door. "Who's there?" he asked. "Martin, the monitor," was the reply. "Dr, Mead wishes to see you at once."