"Moving along now. " Matching action to words, I began moving along the surface, being very careful to keep my grip on the rope and my feet on the ground. I knew for a fact I couldn’t actually hear the shell rotating above my head or feel its vibrations. If there had been any vibration strong enough to be transmitted through the bearings, the whole thing would have already ripped itself apart. Still, my mind inserted a bass hum into the silence.