Instrument for signalling to the prisoners at Pentonville the order of leaving the Chapel

Book illustration showing the instrument for signalling to the prisoners at Pentonville the order of leaving the Chapel, from page 167 of 'The criminal prisons of London and scenes of prison life' by Henry Mayhew and John Binny. The board indicated, by letters and numbers, the rows and stalls to be vacated in turn. As their number and row was indicated, each prisoner would "pull down their cap-peaks, and throwing back the partition-door, hasten from the chapel ... and thus the chapel is entirely emptied, not only with considerable rapidity, but without any disturbance or confusion."