en exact measurement became both possible and
necessary was there any need to apply logic to a given problem.

A logician adds two and two and gets four; an intuitionist multiplies
them and gets the same answer. But a logician, faced with three twos,
gets six--an intuitionist gets eight. Intuition will get higher orders
of answers from a given set of facts than logic will.

Turnbull applied intuition to the facts he knew and came up with an
answer. Then he phoned the New York Public Library, had his phone
connected with the stacks, and spent an hour checking for data that
would either prove or disprove his theory. He found plenty of the former
and none of the latter.

Then he called his superiors at Columbia.

He had to write up his report on the Lobon explorations. Would it be
possible for him to take a six-month leave of absence for the purpose?

It would.

The following Saturday, Dr. Dave F. Turnbull was on the interstellar
liner _Oriona_, bound for Sirius.

* * * * *

If ever there was a Gold Mine In The Sky, it was Centaurus City. To the
cultural xenologists who worked on its mysterious riches, it seemed to
present an almost inexhaustible supply of new data. The former
inhabitants had left everything behind, as though it were no longer of
any value whatever. No other trace of them had as yet been found
anywhere in the known galaxy, but they had left enough material in
Centaurus City to satisfy the curiosity of Mankind for years to come,
and enough mystery and complexity to whet that curiosity to an even
sharper degree.

It's difficult for the average person to grasp just how much information
can be packed into a city covering ten thousand square miles with a
population density equal to that of Manhattan. How long would it take
the hypothetical Man From Mars to investigate New York or London if he
had only the City to work with, if he found them just as they stand
except that the inhabitants had vanished?

The technological level of the aliens could not be said to be either
"above" or "below" that of Man: it could only be said to be "different."
It was as if the two cultures complemented each other; the areas of
knowledge which the aliens had explored seemed to be those which Mankind
had not yet touched, while, at the same time, there appeared to be many
levels of common human knowledge which the aliens had never approached.

From the combination of the two, whole new fiel