The weird shrillness cried less loudly now, and the men listened in strained silence to the go and come of that variable shriek. Musical at times as it leaped from one clear note to another, again it would merge into discordant blendings of half-tones that sent shivers of nervous reaction up the listeners' spines.
"Listen," said McGuire abruptly. "Check me on this. There are two of them, one loud and one faint—right?"
"Right," said Captain Blake.
"Now notice the time intervals—there! The faint one stops, and the big boy cuts in immediately. No waiting; he answers quickly. He does it every time."
"Well?" the captain asked.
"Listen when he stops and see how long before the faint one answers. Call the loud one the ship and the faint one the station.... There! The ship is through!"
There was pause; some seconds elapsed before the answer that whispered so faintly in their ears came out of the night.
"You are right, sir," the operator said in corroboration of McGuire's remark. "There is that wait every time."
"The ship answers at once," said McGuire; "the station only after a wait."
"Meaning—?" inquired the captain.