Fortress Study, Page 1

Fortress Study -- The fourteen drawings (Sheets #1 and 2)
are a list of the defences erected in the Spanish Highlands
by the British army to either stop or delay the forces of
Napoleon during the Peninsular wars of the early 19th and
late 18th century. The artillery firing angles  and ranges
intersected because most of these fortifications were so
constructed on hilltops within cannon rrange of each other.