Like the ineluctable course of a grist-mill water wheel, the profession of milling wheat is coming full circle. My new book on the history of food processing in the United States starts with the story of Oliver Evans, a brilliant inventor hobbled by his humble roots. Evans, a fussy sort of precisionist, reviled the rancid, rock-strewn, maggoty flour that his local Delaware Valley grist mills cranked out. Perhaps even worse to this pioneering process engineer were the product