Read this excerpt for those who may think i exaggerate the contrast between the former river canyon and the present man- made impoundment, i suggest a trip on lake powell followed immediately by another boat trip on the river below the dam. take a boat from lee's ferry up the river to within sight of the dam, then shut off the motor and allow yourself the rare delight of a quiet, effortless drifting down the stream. in that twelve-mile stretch of living green, singing birds, flowing water and untarnished canyon walls sights and sounds a million years older and infinitely lovelier than the roar of motorboats - you will rediscover a small and imperfect sampling of the kind of experience that was taken away from everybody when the oligarch and politicians condemned our river for purposes of their own which rhetorical technique is abbey using in the underlined section of this excerpt?