thout 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 visibly. "The limitations are several," he said.
"In the first place, there is the force represented by _f_ in the
equation. This seems to be entirely dependent on the ... ah ... strength
of the subject's personality. That is if we assume that the process is
at all parallel with the phenomena of psychokinesis and levitation. And
there are excellent theoretical reasons for so believing."

"In other words," Malone said, "a man with a strong will would be able
to exert more force than a weaker-willed man?"

"Correct," Dr. O'Connor said. "And another factor is the time, _t_. What
we are measuring here is the span of attention of the individual--the
ability of the subject's mind to concentrate on a given thing for a span
of time. Many people, for example, cannot keep their attention focused
on a single thought for more than a few milliseconds, it seems. They are
... ah ... 'scatter-brained,' as the saying is."

His expression left no doubt that he included Malone in that group.
Malone tried not to look nervous.

Then Dr. O'Connor scowled. "There is another factor which we feel should
be in the equation," he said, "but we have not yet found a precise way
to express it mathematically. You must realize that the mathematical
treatment of psionics is, as yet, in a relatively primitive stage."

"Oh," Malone said. "Of course. Sure. But this other factor--"

"It is what might be called the ... ah ... _volume_ of attention," Dr.
O'Connor said. "That is, the actual amount of space that can be
conceived of and held by the subject, during the time he is
concentrating."

Malone blinked.

"For most people," Dr. O'Connor said, "the awareness of the space
surrounding them is limited to a few inches of moving space, no more. To
put this in a purely physical matrix: one might say that the
'teleportation field' doesn't extend more than a few inches beyond the
skin of the subject. Thus, it would be difficult to teleport anything
really large unless one were able to increase the volume of attention,
or awareness. However, it is difficult to express this notion
mathematically."

"I'll bet," Malone said.

* * * * *

Dr. O'Connor shot him a frozen glance. "One of our ear