1 : 31680 A note in the bottom left corner of this drawing records the date it was received at the Drawing Office in the Tower of London, where final reduced copies of the plans were made. It is one of the few drawings to make reference to the Tower. A triangulation drawing appears on the reverse, along with an area calculation, referred to in its formal title. Major communication routes are highlighted in yellow, following standard military cartographic convention. Hughes, Herbert J.