1 : 31680 This drawing covers the counties of Gloucestershire, Oxfordshire and Wiltshire, with their boundaries indicated by pecked lines. The Roman road to Bath is tinted yellow to highlight it as a major communication route. A dotted line leading from Sapperton indicates the Sapperton Tunnel, which was opened in 1789. Linked to the Thames and Severn Canal, it was, at that time, the longest tunnel in England. The Sapperton Tunnel enabled boats carry coal cheaply to Cirencester from mines in the north and west. Several trigonometrical points are marked by dots within circles. These were points from which the surveyor took angular measurements to determine the relative locations of prominent features of the landscape. Metcalf, Edward B.