I did so. Though my ear was untrained to distinguish between sounds I could hear just the faintest noise.
Suddenly there came a weird racket. Hastily I looked up at Garrick in surprise.
"What is that?" I asked endeavouring to describe it. "Are they there now?"
"No," he laughed. "That was the moon shining in. I wanted you to hear what a difference it makes. When a ray of the sun, for instance, strikes that 'feeler' over there, a harmonious and majestic sound like the echo of a huge orchestra is heard. The light of the moon, on the other hand, produces a different sound—lamenting, almost like the groans of the wounded on a battlefield."
"So you can distinguish between various kinds of light?"
"Yes. Electric light, you would find if anyone came in and switched it on over there, produces a most unpleasant sound, sometimes like two pieces of glass rubbed against each other, sometimes like the tittering laugh of ghosts, and I have heard it like the piercing cry of an animal. Gaslight is sobbing and whispering, grating and ticking, according to its intensity. By far the most melodious and pleasing sound is produced by an ordinary wax candle. It sounds just like an aeolian harp on which the chords of a solemn tune are struck. I have even tried a glow-worm and it sounded like a bee buzzing. The light from a red-hot piece of iron gives the shrillest and most ear-splitting cry imaginable."
He took the receiver back from me and adjusted it to his own ear.
"Yes," he confirmed, "that was the moon, as I thought. It's a peculiar sound. Once you have heard it you're not likely to forget it. I must silence the machine to that."
We had waited patiently for a long time, and still there was no evidence that anyone had entered the room.
"I'm afraid they decided not to attempt it after all," I said, finally.