any given mass can
be moved. Or, contrariwise, the more mass, the greater mass, that is,
the easier it is to move it any given distance. This is, as you
undoubtedly understand, not at all in contradistinction to physical
phenomena."

"Ah," Malone said, feeling that something was expected of him, but not
being quite sure what.

Dr. O'Connor frowned. "I must admit," he said, "that the uncertainty
as to the constant _k_, and the lack of any real knowledge as to just
what kind of force is being applied, have held up our work so far."
Then his face smoothed out. "Of course, when we have the teleports to
work with, we may derive a full set of laws which--"

"Never mind that now," Malone said.

"But our work is most important, Mr. Malone," Dr. O'Connor said with a
motion of his eyebrows. "As I'm sure you must understand."

"Oh," Malone said, feeling if he'd been caught without his homework,
"of course. But if you don't mind--"

"Yes, Mr. Malone?" Dr. O'Connor said smoothly.

"What I want to know," Malone said, "is this. What are the limitations
of this--uh--phenomenon?"

Dr. O'Connor brightened up thoroughly. "Well, theoretically," he said,
"there do not appear to be any limitations. However, practical
limitations do exist. If the process is at all parallel with
psychokinesis, or with levitation"--he stared at Malone, as if daring
him to say that it wasn't--"if that parallel exists, then the subject
is mentally limited by his own physical strength."

Malone said, "What?"

"Try and be patient, Mr. Malone," O'Connor said calmly. "Please. As I
was saying, the subject is limited by his own physical strength. In
other words, he cannot move psionically any subject larger than he can
lift physically. This appears to be a psychological limitation
which--"

"Oh," Malone said. "You mean he couldn't carry off a building, or
anything like that?"

"Of course not," Dr. O'Connor said. "Nor, as a matter of fact, could
he carry off anything that was securely bolted down. I hope you follow
me."

"I think so," Malone said. "But look here. Suppose you handcuffed him
to, say, a radiator, or a jail cell bar."

"Yes?"

"Could he get _away_?"

Dr. O'Connor appeared to consider this with some care. "Well," he said
at last, "he certainly couldn't take the radiator with him, or the
cell bar. If that's what you mean." He hesitated, looked slightly
shamefaced, and then went on: "But you must realize that we lack any
really extensiv