ving alike, etc., the mass of light can't be monochromatic. Therefore
perfect interference is impossible.

"The way that relates to the problem in hand, is that we can't possibly
destroy his energy. We can, as we do in the crumbler stunt, change it.
He can't, I suspect, put too much power behind his crumbler, or he'd
have crumbling going on at home. We get a slight heating from it,
anyway. Into the bargain, his radio was after us, and his neutrons
naturally carried energy. Now, no matter what we do, we've got that to
handle. When we fight his crumbler, we actually add heat-energy to it,
ourselves, and make the heating effect just twice as bad. If we try to
heterodyne his radio--presto--it has twice the heat energy anyway,
though we might reduce it to a frequency that penetrated the ship
instead of all staying in it. But by the proposition, we have to use as
much energy, and in fact, remember the 80% rule. We've got to take it
and like it."

"But," objected McLaurin, "we _don't_ like it."

"Then build ships as big as his, and he'll quit trying to roast you.
Particularly if the inner walls are synthetic plastics. Did you know I
used them in the 'S Doradus' and 'Cepheid'?"

"Yes. Were you thinking of that?"

"No--just luck--and the fact that they're light, strong as steel almost,
and can be manufactured in forms much more quickly. Only the outer hull
is tungsten-beryllium. The advantage in this will be that nearly all the
energy will be absorbed outside, and we'll radiate pretty fast,
particularly as that tungsten-beryllium has a high radiation-factor in
the long heat range."

"What does that mean?"

"Well, ordinary polished silver is a mighty poor radiator. Homely
example: Try waiting for your coffee to cool if it's in a polished
silver pot. Then try it in a tungsten-beryllium pot. No matter how you
polish that tungsten-beryllium, the stuff WILL radiate heat. That's why
an IP ship is always so blamed cold. You know the passenger ships use
polished aluminum outer walls. The big help is, that the
tungsten-beryllium will throw off the energy pretty fast, and in a big
ship, with a whale of a lot of matter to heat, the Strangers will simply
give up the idea."

"Yes, but only two ships in the system compare with them in size."

"Sorry--but I didn't build the IP fleet, and there are lots of tungsten
and beryllium on Earth. Enough anyway."

"Will they use that beam on the fort? And can't we use the thing on
them?"