No one knows how high the effect goes, or how deep. Birds avoid the airspace over the sentinels, wheeling and turning with a high pitched scream rather than flying across the line of stones. Mussels and barnacles don’t cling to them, and there are no minnows living in their too-dark shadows.

Last year Mike and I decided we were going to take his sailboat out, see how far the parade extends, and sail around the end. Mike’s a better sailor than me – but I think things through.

“Do we really need to bring all those galley supplies with us?” he’d ask, every time I passed him on the pier, loading up. “We have fishing gear, we’ll be fine for just a few days.”

“We have no idea how long we’ll be out, let’s make sure we’re prepared,” I’d respond, patiently.

It’s been a long time, I miss Mike a lot, but I’m glad to have his supply of water.