Survey of the Great Lakes
In 1814-1816 the first Admiralty Survey of Lake Ontario and Georgian Bay was undertaken by Admiral William Fitzwilliam Owen, after whom Owen Sound is named. His successor, Admiral Henry Wolsey Bayfield, completed the first survey of Lakes Erie, Huron and Superior in 1817-25. The work of these officers rendered great service to Canada by increasing the safety of navigation.
Plaque via Alan L. Brown's site Ontario Plaques. Full page here.