"Nothing! Don't be foolish!" said my uncle. "Nothing can hurt me!"

I went back to the laboratory, and, having nothing further to do, sat down to wait for his coming.

Again came the explosion, followed by the same cry.

I started up and, before I thought, I cried aloud, "You're not hurt, are you?"

The door opened suddenly, and my uncle came out, looking very much excited.

"Dick!" said he, "go home. Here is your bag. I shan't need your help to-night."

I took what I thought was my bag, and went home to my room.

When I lighted my student-lamp I saw that, instead of my traveling-bag, my uncle had given me an old, dusty, wrinkled and battered leather satchel, which looked as though it might be a century old.

I laughed, and tried to open it. It was locked. After puzzling over the lock until I was tired, I opened my closet door and flung the satchel upon the highest shelf.

"To-morrow," said I, "I'll exchange it for my own bag."