The soldier in question, in the uniform of an infantry regular, sat facing them, beside a stout elderly gentleman. Opposite the first soldier was a second, in a similar uniform; and sharing the seat with the latter, and facing the old gentleman, was a decidedly pretty young girl.
It was the first soldier’s left hand, however, which attracted the boys’ particular attention. Resting in his lap, and partly concealed by a newspaper, the hand was so doubled that the thumb stood upright. And this latter member was bobbing and wagging up and down, now slowly, now quickly, in most curious fashion.
“Perhaps it’s St. Vitus’ dance,” ventured Jack.
“But that affects the whole body, or at least the whole limb, doesn’t it?”
Jack, who sat next the window, leaned slightly forward. “The other soldier is watching him,” he said. “Maybe the fellow with the wiggling thumb is out of his mind, and this one is taking him somewhere. He is watching his hand.”
Silently the boys continued to regard the curious proceeding.
Suddenly the thumb became quiet, there was the rattle of a paper in the hands of the second soldier, and in turn his thumb became affected with the wagging. In a moment the boys understood.
The two soldiers were army signallers, and were carrying on a silent conversation, using their thumbs as they would a flag.
Jack and Alex looked at one another and laughed softly. “We’re bright, eh?” Alex remarked.
“Let us watch when the other starts again—we can’t see this chap’s hand well enough—and see if we can’t read it,” suggested Jack. “That one-flag signal system is based on the telegraph dot and dash code, you know. And it’s not likely they are speaking of anything private—only amusing themselves.”