Fay climbed upon the table and adjusted the hollow lens. He blocked one edge so that it could be shifted. He raised and lowered the frame upon which it rested. A sudden flash, followed by a small cloud of smoke, indicated that the focused rays had touched the woodwork at the edge of the trapdoor.
“Hotter than any electric-arc,” he said. “Now watch when I get the point of light on the vanadium. This is the same scheme old Archimedes used centuries ago to burn ships.”
“I thought he used mirrors—”
“Perhaps he did. I’ve got mirrors to heat the vanadium and keep the temperature of the plate high. Our chief difficulty will be in the loss of heat due to radiation. The—”
Saidee Isaacs sprang back from the opening. A sizzling sounded. Blue smoke filled the room. The plate was being melted along the line Fay had drawn. The movement of the sun, from east to west, was changing the position of the ray.
Fay climbed to the table and adjusted his curved mirrors. He focused them about the spot of whiter light that coned down from the hollow lens. The California sun is bright. The skylight did not require opening.
“We’re getting on!” he exclaimed. “I’ve gone through the first plate and reached the fireproofing. I’ll have to change the lens and spot across the oblong. My east and west lines are easy. The cross lines will take some time.”
“How about the heat melting the paint in the vault?”
“The asbestos layers between the plates will prevent that. See! We were lucky that ‘The Black Cougar’s’ was both fireproof and burglar-proof. But then, Saidee, they make them all that way.”
The girl shielded her eyes and leaned over the opening in the floor. A narrow channel showed where the spot of light had cut through the first vanadium plate. The fused metal formed bubbles along the edges. Beneath the bubbles was the white fireproofing material.