He looked up at the open safe. It was still empty. Well, by golly, he'd see whether this was a hoax or not. He pulled his gold-plated desk pen out of its crystal holder, took a piece of office stationery, and wrote: _Dear Mr. Guelph_: _I'm very much interested in your proposition, but I would like to have you explain a little bit more about it._ _Very truly yours, Peter Merton_ He folded it and put it in the safe. Then he sat down and watched it. He watched it for fifteen minutes before he decided that nothing was going to happen. Finally, he walked over and took out the paper. It was the same as it had been when he put it in. He looked back at the plastic sheet. Aha! It said: "In order for the Time Transfer Field to work, it must be surrounded entirely by thick metal." He put the note back in, and this time he closed and locked the door. Three minutes later, he opened it again. This time, there was another folded sheet of plastic. It said: _Dear Mr. Merton_: _Understanding Time Transfer is very simple. Of course, the science of your time would be unable to build such a machine, but what happens is essentially this: If you put something in your metal box, we can pick it up and bring it to our time. However, there must be an equivalent exchange of matter, so we have to send something to your century, too. This must be done in accordance with the Law of Entropy._ _What we need mostly are historical documents; newspapers, books, and magazines of your era. Please send only factual material; no fiction. We will want fiction later, but not now._ _Here is a list of things we would like to have._ Peter read down the list and blinked in amazement at some of the things. The letter ended with: _In return for this, we will send an equal weight of some of our old museum pieces of paper. Papers like the one we took from you; things called "money." Will this be satisfactory? Here is a sample._ _Yours very truly, Rolath Guelph._ Money? Peter looked at the bill that was enclosed. It was a five-hundred-dollar-note! And they said they would exchange pound for pound! That meant that for one pound of old newspapers, he would get one pound of banknotes! It sounded screwy, but Peter Merton was not a man to argue. If it worked, fine; if it didn't, what could he lose? Peter jammed his hat on his head, folded the list and the five hundred dollars in his pocket, and strode out the door. He stopped in the outer office at the desk of Miss Simmons, who was typing up some letters. "Come along, Miss Simmons," he said. "Get your hat; we have some things to do."