The professor replaced his own mask and conducted the woman into the interior of the laboratory.
"I will show you," said Professor Burr.
She saw before her now, on long metal shelves which appeared to be delicately poised on fine scales whose balance was registered by hair-line indicators, two small metal cages.
Professor Burr stepped over to a row of common cages set along the wall. There was a small menagerie there, guinea pigs—the martyrs of the animal kingdom—rabbits, monkeys, and some cats.
The man of science reached in and dragged out a mewing cat, placing it in the right-hand cage on the strange table. He then obtained a small monkey and put this animal in the left-hand cage, beside the cat. The cat, on the right, squatted on its haunches, mewing in pique and looking up at its tormentor. The monkey, after a quick look around, began to investigate the upper reaches of its new cage.
Over each of the animals was suspended a fine, curious metallic armament. For several minutes, while the woman, puzzled at how this demonstration was to affect the rescue of her condemned son, waited impatiently, the professor deftly worked at the apparatus, connecting wires here and there.
"I am ready now," said Burr. "Watch the two animals carefully."
"Yes, yes," she replied, faintly, for she was half afraid.
The great scientist was stooping over, looking at the balances of the indicators through microscopes.