“A burning-glass,” said Fay, “does not necessarily need to be solid. I intend to paste the edges together with plaster of Paris and fill the whole thing with clear water.”
“Going to make a sun-motor?” asked the artisan.
“Something like that. Wrap it in tissue paper. I don’t want to break it on my way to Pasadena.”
Having thus thrown off all clues, Fay carried the hollow lens to the studio. Saidee Isaacs had received the package, left it unopened on the dark-room floor and pinned a brief note to the table in the reception-room.
“Gone for the day. Have a headache. Will be at my hotel if you want to call me up.”
Fay destroyed the note, took off his coat, tie and collar and started to work rigging the mirrors and the hollow lens upon a scaffolding beneath the skylight.
It was shortly after midnight when he finished adjusting the device to his satisfaction. He went to the window, peered out, saw the night-watchman talking with a uniformed policeman on the street-corner, and smiled with some slight degree of satisfaction.
The hole he cut directly over the vault and beneath the scaffolding was aimed to miss two floor-beams which he had located by a line of nail-heads. He reached, before dawn, the first and upper plate of vanadium steel which protected the vault. He cleared a square space and emptied the plaster and shavings in a box.
A neat trapdoor, hinged on the lower side, was the work of a silent hour wherein he used screws instead of nails on the hinges. He covered the floor with a matting, swept out the corners for chance evidence and washed up.
The arrangement of mirrors, the hollow lens, which had not yet been filled with water, the adjustable scaffolding beneath the skylight, all resembled a part of a photograph outfit designed to intensify the overhead rays of the California sun. The lens reminded Fay of a large goldfish bowl.