SOURCE TEXT = George Stevens: Three years in the Sixth corps. A concise narrative of events in the Army of the Potomac, from 1861 to the close of the rebellion, April 1865 (1866) [p.272-273]
"Contraband" is a wartime term for people who had escaped from slavery & crossed over to the Union side. For the fascinating history of the term, and some cool period images, a good starting place is the Wikipedia entry. Edwin Forbes sketched some "contrabands escaping" near Hanover, Virginia:
↑ Edwin Forbes: Contrabands escaping (1864)
So you mean all this time while Colby & Roe have been narrating their observations of camp comings & goings -- and I've been drawing them, too -- we've been neglecting this "characteristic feature" of the situation? Refugees "all along our Rappahannock picket lines" ... "great numbers" ... "constantly applying for permission..."?! That's quite an omission.
Stevens is unequivocal, and the fact that he published this account in 1866, so soon after the war, lends it the same credence I'm granting Colby's wartime letters. It's a contemporaneous eyewitness account set down without the benfit of hindsight & long-after revision.
This is indeed an education for New Englanders like Freeman Colby, whether he records it in his letters & diary or not. Now that we know they're there, we need to find some recorded firsthand accounts BY these "refugees of slavery"...