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_What we need mostly are historical documents; newspapers, books,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,