They are already in operation, sending their defensive waves against the heaviside layer.
"Invaders from the Infinite"
John Wood Campbell
The stars visible through the laboratory windows winked violently in the disturbed air of the heaviside layer, for the molecular ray screen was still up.
"Invaders from the Infinite"
John Wood Campbell
They were in the atmosphere, screaming through it as their relux glowed instantaneously in the heaviside layer, then was through before damage could be done.
"Invaders from the Infinite"
John Wood Campbell
