"But just what is The Ray?" I asked.

"We do not know that either, nor how it is made. We only know that it destroys the oxygen carrying power of living blood. If it were an emanation from a substance like radium, they could have fired it in projectiles and so conquered the earth. If it were ether waves like electricity, we should have been able to have insulated against it, or they should have been able to project it farther and destroy our aircraft, but The Ray is not destructive beyond two thousand metres in the air and hardly that far in the earth."

"Then why do we not fly over and land an army and great guns and batter down the walls of Berlin and he done with it?"