reaches the second submarine they impinge on the disk of the microphone when it vibrates; this varies the battery current flowing through the microphone and you hear the dots and dashes in the receiver.
Now when a U-boat, or any other kind of a power vessel, gets within a certain range of the chaser the hum of the machinery in her sets the hull into vibration and you can hear it in the receivers. So, you see, whether a U-boat is afloat or submerged it is pretty hard for her to escape the eternal vigilance of the chaser.
We had received word by wireless that a U-boat had been sighted about a hundred miles off the coast and that she was one of gigantic size. We swept our area with great zeal, the lookouts in the crow’s nest being changed every two hours; the gunners were at their guns ready for instant action and John Paul Jones Boggs, the other operator and I took turn about listening-in.
I don’t want to brag about myself but I found out a long time ago when I was a kid operator back home that I had a more sensitive ear than any of the other fellows, that is, I could differentiate dots and dashes and take down mes-