Alice Trulock in her Chamberlain biography IN THE HANDS OF PROVIDENCE describes the same scene on pages 124 - 126 "When darkness fell and the full moon rose, the bands struck up and the colors were unfurled again. Farmers and townspeople came out of the houses and to the roadside, hailing their deliverers and bringing water and food. Young women, all made to seem beautiful by the soft light, sang and waved handkerchiefs, and flirted with young staff officers, who lingered to talk in low, hurried tones and sometimes, perhaps, bent down from their horses to steal a kiss. A group of girls by the wayside began singing "The Star Spangled Banner", and Strong Vincent, inspired by the most magical mood, looked at his country's flag. Baring his head he, declared to those riding with him:"What death more glorious could any man desire than to die on the soil of old Pennsylvania fighting for that flag?"
"As the columns marched on, a staff officer appeared from the shadows and whispered a few words to the leading officers. Vincent announced a message from General Barnes that the still popular McClellan was at the head of the army, after which cheer after joyous cheer exploded from the throats of the men and the pace picked up. Catching the enthusiasm, Vincent raised his hand in a wave and exclaimed, "Now boys, we will give 'em hell tomorrow."
Mac and Strong Vincent at Gettysburg
Nick Korolev, of the McClellan Society, was good enough to hunt up another Mac at Gettysburg story, and it's a good one with a rumor attribution given to General Barnes. When it rains, it pours!