Sentinel Butte, Again How rainfall chisels away the rolling prairie beneath the capstones. Sentinel is a mesa, the high table of western North Dakota, first thing you see when driving from Montana. I crashed at Exit One, named Buffalo Gap, slept on the tailgate of my first Ford Bronco, waking to calves poking their heads through barbed wire to slurp my socks. I was the nearest salt lick. Amazed I’ve now put six decades behind me and driving home from Bozeman, Billings, Red Lodge, Sentinel Butte filling my bug-stained windshield, sometimes I wish that I were in my twenties. White…