From the Richmond Sentinel, 5/19/1863

An Undermining Set. - A number of prisoners in Castle Thunder, not relishing the idea of remaining in even that delightful place during the summer months, have lately been performing undermining operations on an extensive scale, which would, perhaps, have proved successful, had not some of their more contented associates exposed the plot. They gained access to a room below the surface of the street by cutting through the floor, and had excavated a large passage leading towards open air & freedom, when the plan was frustrated. If a prison were made equal to a palace, some reprobates would be discontented with it.