Thompson shook his grizzled head, as if, to rid it of a nightmare. “You took an awful chance. Suppose it had cracked.”

“Cracked ! In the name of Planck cannot you understand that the Lanson Screen is not matter that can crack?” The other spread veined, pudgy hands. "It is the negation of all energy, a dimensionless shell through which energy cannot penetrate. And since matter is a form of energy — ” The physicist checked himself, shrugged. “But what’s the use? I cannot expect you to understand. Besides myself there are perhaps a dozen in the world who could comprehend, and none is an American. Enough for you to know that I had to be inside to operate the B machine that cut the negative force the A apparatus set up. From outside it could not be done. The Screen would have remained forever and you would not be convinced there had been, no effect of your bombardment within it...”

“Don’t you understand yet that once the Lanson Screen is erected all within is as absolutely cut off from the rest of the universe as if it were a different space, a different dimension? Nothing can penetrate within — electricity, wireless, the cosmic rays, the sun’s radiations. Nothing!"

(Lanson Screen from 'The Lanson Screen' by Leo Zagat)