Charles Lindbergh's achievement in finding his way alone from Long Island to an airfield outside Paris deserves a moment's consideration. Maintaining your bearings by means of dead reckoning means taking close note of compass headings, speed of travel, time elapsed since the last calculation, and any deviations from the prescribed route induced by drifting. Some measure of the difficulty is shown by the fact that the Byrd expedition the following month--despite having a dedicated navigator and radio operator, as well as pilot and copilot--missed their expected landfall by two hundred miles, were often only vaguely aware of where they were, and mistook a lighthouse on the Normandy coast for the lights of Paris. Lindbergh by contrast hit all his targets exactly--Nova Scotia, Newfoundland, the Dingle Peninsula in Ireland, Cap de la Hague in France, Le Bourget in Paris--and did so while making the calculations on his lap while flying an unstable plane.