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A refrigerator freight car, circa 1870.
Credit: Courtesy of Larry Handy, www.eastcoastbrew.com
Easily identifiable by their telltale roof hatches, "ice reefers" seemed to improve every year as they underwent constant redesign. Relying on the fundamental principle that warm air rises and cold air sinks, loads were either hung, stacked, or raised on pallets, so the cool air would always circulate around the load.