Here Miss Knowles interrupted him, eagerly.
“I think I see what you mean,” she said. “These unusual strings upon the harp, this great strengthening of the frame, means that it is keyed to this inaudible pitch. That some one outside has an instrument of some sort keyed in unison; and when the harp string is touched, the other vibrated in sympathy.”
“And that these vibrations, made in long or short waves, or in groups, much, perhaps, as the telegraph code is made, formed a ready means of communication.”
Mr. Scanlon seemed appalled.
“Well,” said he, after a short pause, “I think I’ve absorbed the most of it. But I’m not sure. However, there is one thing I am sure of, and that is that I’ve got a cabinet sized photograph of the party who’s got the other instrument. That’s what Alva had that night on the hilltop when I saw him sitting in the moonlight. He was exchanging silent talk with Schwartzberg.” Then an idea seemed to strike him, and he frowned again. “There is one thing that I don’t quite get. And that is: If these vibrations, or tones, or sounds, whatever you call them, were too high to be heard, how did the receivers of them make them out?”
Ashton-Kirk shook his head.
“As to that,” said he, “I am not prepared to say just now. A further search into the thing might bring it out, but I’m not sure. But this I will say: The sense of touch is marvellously sensitive in some people; one every now and then hears some wonderful story with regard to it. Fine, delicate hands may be the answer to your question.”
“Another thing,” said the girl. “Why was the wind required to always be from the direction of the person sending the vibrations to Schwartzberg? You’ll say to carry them. But what of the answer to them? Would not the wind which carried the vibrations from one quarter hold back those sent from the one opposite?”
“Only in part, unless the wind was very strong. And I think if you can remember the nights upon which this means of communication was used, they were fairly calm. The fact that the wind at the time of the signals was always from the direction of the person outside might be explained by that person’s superior knowledge of the medium in use. Having a more perfect understanding of it, he was the more able to read its fainter manifestations.”
Here a small clock hurriedly struck the hour of nine. And Ashton-Kirk looked at Scanlon.