Thank you for the information about Wilders Lake. Sorry I haven't responded sooner. My husband and I were recently in Ontario and had an opportunity to see the lake. We also found the property where my husband's great-grandfather, Alexander Hamilton, first settled. The property is right on the lake. One of his sons (David) and grandsons had a picnic area on the lake that was visited by many from all around. They also ran a boat rental on the lake.
There are a couple pictures of the lake and the marl "mill" in the History of Egremont book.